“Bella, I know it’s not the point, but where is your jumper from?” This was a reply to a post I put up on Instagram about the horrors of antidepressant withdrawal. I respond with the details, mildly flattered, but slightly despairing. After decades of not talking about my mental health issues, I started an Instagram account (@mackie_bella) hoping to talk more honestly about them, but maybe when everyone has their own struggles they don’t want to be burdened with yours. Why would you want to watch someone else moan on the morning commute when you could gaze at a lovely fluffy jumper to cheer yourself up? I would choose the jumper myself most days.

I have become somewhat well followed on Instagram at a time when the platform is being hugely criticised. Social media influencers are widely scorned for showing off unattainable lifestyles, promoting irresponsible products, such as slimming teas, and being disingenuous about what’s real and what’s staged for effect. Websites have sprung up where those who are fed up with the polished images can call them out, sometimes brutally.

Like everyone else who uses social media, I have a complicated relationship with it. It’s become common to complain about our online spaces, we all try to articulate the myriad ways in which we find it draining, toxic and unnatural. We scroll and swipe and get angry with ourselves for wasting time staring down at our phones when we could be doing something worthwhile. But, equally, social media is now one of the main ways people communicate with each other in the modern world. To ignore it is to miss out.

Four-legged friends: ‘At first my husband Greg (who is very funny online) directed people to my sparse new account.’ Photograph: @bellamackie

Most will vaguely recognise the term “influencer”, which, roughly, describes a person who uses social media to promote a lifestyle or aesthetic. In other words, someone who tells others what stuff they should buy. Like a lot of people, I’ve felt uneasy about this growing phenomenon. Impossibly pretty (and usually white) women giving you a tiny glimpse of their carefully curated lives while simultaneously offering you 15% off the boots they’re wearing. It’s an exercise in aspiration – buy these boots and be happy like me.

Despite my unease, I have acquired 130,000 followers on Instagram, so now I’m trying to walk a line between flogging teeth-whitening kits and using the platform solely to preach about mental health. Can you be an influencer and not become a bit of a monster? The line between the two seems fairly direct.

I really love Instagram. I loved it from the moment I signed up – a place to show off photos that meant something to me. A gallery of my life, but with strictly controlled privacy settings. After a rough experience with a stalker, I didn’t understand those who felt comfortable showing off their lives to strangers.

All of that changed when my first book, Jog On, a memoir about mental illness, was about to be published. It was suggested that I create an account to share book news, so I duly did, thinking it would be a temporary space to throw promo into the world before retreating back to my private account.

Except, and I should have known this, you have no idea what will happen on social media. My husband Greg James (a presenter on Radio 1) directed people to my sparse new account. Suddenly I had a few thousand followers – and the book wasn’t even out for another fortnight. Those numbers have continued to rise over the past year and I’ve come to realise how Instagram could become a full time occupation.

Mirror, mirror: ‘I constantly wonder how authentic I’m being.’ Photograph: @bellamackie

People make millions from influencing. It’s a job now; you can’t hold back that tide. But while there are a million posts to roll your eyes at, I’ve learned that there are wonderful communities, too. So many people use social media to promote specific causes or to grow their interests. Politicians bypass traditional media and go to Instagram to speak directly to their supporters – Alexandria Ocasio-Cortez, for example, has 4m followers.

I wasn’t using social media to run for office. Neither was I part of Gen Z, who’ve grown up online, and are savvy about the worth of their “personal brand”. I fell into this by accident, which might well be the best way to do it. Along the way, here’s a few things I’ve learned.

It will envelop you unless you’re careful

Spend too much time on social media and you enter a weird realm where you’re speaking to strangers more than your actual friends. Within a week of the book coming out, thousands of people had got in touch to talk to me about their own experiences. They wanted to tell me their own stories of panic, sexual assault, grief and pain. I responded to every one, trying to show sympathy and support. I felt an enormous weight of responsibility when a new message pinged up on my screen. How could I ignore a person sharing their biggest problems? And this made my own mental health plummet. Instead of celebrating the book’s release, I spent most of my time crying, trying to push back against an onslaught of intrusive thoughts and a looming sense of doom.

But it’s no use having a public Instagram account and choosing not to engage with the people who follow you. The internet has demolished any lingering notion that you can create something, release it into the world and walk away. The trick is knowing where to draw the line, so that you can maintain your own equilibrium.

Boundaries on social media don’t exist. I will talk to as many people as possible about mental health (it’s usually hundreds a week). But I can’t answer people who need relationship advice, and won’t answer those who ask me whether I’m going to have children. I shouldn’t have to tell you where to find the perfect profiterole when Google exists. It might all be coming from a good place, but the internet makes people feel entitled to ask the most personal of questions, and it can get overwhelming.

It always comes back to numbers

Instagram has always been ruled by the number of likes a photo amasses. I’ve learned that I cannot control what people want to look at. My plan was to post mental health information only. But I once posted a photo of myself clad in bright colours, explaining that, when in a hole, I try to dress in a hopeful way. It was an attempt at conveying that I was feeling very anxious and was worried about appearing vain or vapid. And indeed one person told me off for using my account in the “wrong” way and promptly unfollowed me. But otherwise, the reaction was fairly positive.

I described my approach to dressing as “always be jazzy”, and added the abbreviation ABJ. Things take on a life of their own on social media. I now get sent photos from women who have bought leopard print shoes or sequinned headbands, asking me if they’re ABJ enough. It’s ludicrous. But the idea that I might have made a few people feel more confident is a lovely thing. Even if it means that posts about my clothes will always trump anything I put up about politics. Like I said, sometimes you just want to see a fluffy jumper.

You can build a community around anything

When I started my account I made the decision not to follow anyone who might make me feel bad about myself. So I followed runners, farmers, mental health experts and book obsessives. I muted all suggestions on the homepage for accounts that showed off impossibly perfect people or lifestyles. And in that spirit, I think hard about whether I’m being too glossy myself.

Clinical psychologist Dr Emma Hepburn, who posts under the handle @thepsychologymum, is smart about this. “It’s important to recognise whether what you are consuming is having a positive or negative influence on you,” she says, “and you need to actively manage this if it is having a detrimental impact. For example, limiting time on social media, or taking control of the types of account or content you are viewing, and ensuring any advice you are following is provided by someone who’s actually qualified to give it.”

Unto those that have, more shall be given

I once mentioned that I keep oatcakes in my purse in case I get anxious and I got sent a Brexit-stockpile worth of them. I posted a photo of my lawn and was offered a free mower. I’ve been asked to go to the launch of a new soap, offered a portrait of my dog. One company tried to get me to accept a free ear piercing if I filmed it live. Very much opening-of-an-envelope stuff, but some people must accept it. While it feels nice initially to be offered free things, everything is a quid pro quo. Accept a complimentary thong made of gummy bears and the expectation is that you’ll post a photo of your arse in it. The quid isn’t normally worth the quo.

I’ve accepted one paid-for posting in the year I’ve been using the account. It was a dilemma, even though it was for a store I’ve loved for years. Maybe it knocks me off my high horse a bit to accept the influencer dollar. Perhaps if I had a full time job I’d never have considered it, but I’m a freelancer and paid irregularly. I ended up being at ease with it since it allowed me to spend time writing about mental health on Instagram without feeling horrendously guilty that it was eating into time spent doing paid work. We live at a time when being self-employed is on the rise, and I find it hard to understand the level of animosity directed at women who earn money on social media. Again, there’s always a line. I’ve seen people promote products they’d never use, and that disconnect ends up showing. You see a celebrity gushing about cheap sunglasses and begin to wonder about their intentions. Which brings me neatly to my next point…

None of it is completely real

The search for authenticity on social media is constant, but futile. After years of heavily curated feeds and aspirational content, there is now a trend where popular women on Instagram (52% of users are female) take off their makeup and confess that their previous photos were all just a veneer. But then, as New Yorker writer Jia Tolentino noted in her book Trick Mirror, such a woman “will take a week long break and then, almost always, she will go on exactly as before”. The act will inevitably be called brave by some who don’t realise that this show of authenticity is no more real than the previous images.

I constantly wonder how authentic I’m being, how much of my real self I’m showing. I’m more cynical in real life than I am on Instagram, and definitely not as outgoing. I don’t post photos of my family or friends. Does that make me fraudulent, or is it impossible to really be yourself through a filter? And equally, why should you try to be the most accurate version of yourself for a bunch of strangers? The disconnect shouldn’t be jarring, but you’re entitled to hold some of yourself back, or enjoy being bolder online than you might be usually. Not everything that can be shown needs to be.

People want to be nice

The most surprising thing I’ve found from a year of minor Instagram popularity is that people can be wonderful online. I’m well aware this isn’t the case for everyone, but it gives me hope that the relatively new world of influencers might be a more positive place than people fear. I’ve spoken to thousands of people I’d never have encountered, talking about mental illness, getting and giving tips for when anxiety ramps up. I’ve had people send me recipes, poetry and in one case, a glittery bowtie for my dog. The best books I read last year were ones I found through Instagram. In return, I’ve sent strangers books, signposted articles I think are important, spent hours talking to people with anxiety, and highlighted campaigns that need more attention.

It’s a choice whether to entertain or exploit. I’ve enjoyed learning what feels good and what feels grubby. Sometimes I’ve tipped into shallow waters with fashion posts, then spent days talking about sexual harassment. Despite finding it tricky to walk the line I’ve set, it’s made me more confident about my voice. I’ll happily talk about my own intrusive thoughts on live video, but a few years ago I couldn’t have told my mum about them. I often feel vain and silly fiddling about online, and I’ve had sneery comments from acquaintances about it. I understand that reaction – the narcissism of Instagram can’t be denied. But when someone tells me that a mental health post made them finally seek help, I think I’m doing something worthwhile. My private account has been neglected for months. The audience I have might get bored and move on, or I might retreat from it one day. But for now, I’m enjoying the absurdity of it all, the lovely nonsense. Hopefully, as long as I remember that, I won’t become too monstrous in the process.

Order a copy of Bella Mackie’s book Jog On (Harper Collins, £8.99) from guardianbookshop.com for £7.91