I envy men who have premature ejaculation: at least they can finish. I’ve always had difficulty ejaculating during sex; when I lost my virginity, my partner didn’t believe it was my first time because I lasted so long. The problem has only got worse as I’ve got older, and these days, I often lose my erection after about 10 minutes due to the stress of knowing I won’t orgasm. In my whole life, I’ve only had sex five or six times without this being an issue.

At 35, I discovered the term traumatic masturbatory syndrome online. I think this is at the root of my problems; my early experiments with masturbation may have reduced the nerve function in my penis. I also worry that my 5in penis is smaller than average. My first girlfriend told me it was inadequate, and in my 20s, another girlfriend laughed about it in front of several mutual friends at a party.

As a result of this insecurity, and my issues ejaculating, my sex life with my first wife was almost nonexistent. This led to me sleeping with a friend of hers. After a messy divorce for each of us, we are still together 20 years later.

I am lucky that my current wife realises my struggle to ejaculate frustrates me, too, and does her best to understand that my problem is not anything to do with my feelings towards her. She has encouraged me to seek medical help, and I’m now prescribed medication for erectile dysfunction. It helps me maintain an erection, but I still find it nearly impossible to finish. I’m exhausted.

• Each week, a reader tells us about their sex life. Want to share yours? Email sex@theguardian.com

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