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It's a common refrain from couples who've split up: "Somewhere down the line, we became more like roommates than spouses."

The truth is, passionless, sexually unsatisfying marriages don't get that way overnight. Below, relationship experts offer up seven signs you're on your way to a sexless marriage -- and tips on how to reignite the passion between you and your partner.

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Let's start with the obvious. If you can't remember the last time you had sex with your spouse -- or you're only having special-occasion sex (birthdays, vacations, anniversaries) -- it's not a good sign. Maybe it's been months, maybe it's been years -- but the more time passes, the harder it becomes to revive your sex life, said Tammy Nelson, certified sexologist and sex therapist and the author of Getting the Sex You Want.

"Biologically, the body stops producing the sex hormones that make you aroused, especially if you have gone long periods without it," she explained. "And then you may start to feel like you aren’t interested in it anyway."

So how do you take sex off the back-burner? Schedule in sex dates. It may seem like the least sexy plan of attack but it will likely get you and your partner back on track, Nelson said.

"The more sex you have, the more sex you want," she explained. "Having sex can jump start the engine and it may even remind you that you enjoy making love to your partner. You might get out of the roommate rut and start to do it more often."

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Forget your lackluster sex life. You're not even touching these days. You knew the PDA-filled, heady early days of your romance weren't going to last but at this point, you're not even embracing before week-long work trips. The key to making touch a priority again is to reach out to your partner without intentions, said Nelson.

"Enjoy a simple and sensual night together with candles, where you're just watching TV," she said. "Sit next to each other, hold each other, lie in each others lap, stroke each other’s hair. Get the dopamine going again. If the mood is right you might take off each other’s clothes and have sex -- or you may just end up watching another movie. But just touching again is important."

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You may share the same bed, but that's about all you share with your spouse lately. When your lives rarely intersect -- and everything but your marriage takes priority (kids, work, travel, friends) -- there's little time left for sex, said Susan Krauss Whitbourne, a psychologist who writes Psychology Today's “Fulfillment At Any Age" blog.

To get back on the same page, make an active decision to drift back together, Whitbourne said.

"You may live hectic lives, but you need to build into your calendars time to talk face-to-face, without distractions -- preferably daily," she said. "Your dinner hour may be taken over by the feeding schedules of your kids but find a way to have alone time even if it's just sharing a late-night glass of wine.

Eventually, Whitbourne said, "you'll realize you got together for a reason, and if you dedicate time to each other, those reasons will become very apparent again."

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If sex is painful or uncomfortable for you or your spouse, it's understandable why it's gotten the short-shrift lately. If it just doesn't feel right, the "the problem may be one of technique," said Susan Heitler, a psychologist and the author of the marriage betterment program Power Of Two Marriage.

"Getting informed can help this problem," she said. "For instance, if you're a woman, sometimes a warm-up before you hit the sack -- an exercise to get the blood flow going or a warm shower -- can enhance your responsivity from the get-go of couple contact. And if you feel sexually aroused, it will likely be contagious and enhance your spouse's arousal as well."

If the problem is pain or dryness brought on by menopause, Heitler said medical attention may be able to remedy it. Check with your doctor if you suspect that's the case.

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If you (or your partner) have developed feelings for someone else -- a co-worker you're inexplicably drawn to, for instance -- you may start to feel less invested in your marriage. It may not have turned physical yet, but the mental energy involved in an emotional affair -- and being physically attracted to someone who's not your spouse -- takes attention away from your bedroom, said Krauss Whitbourne.

"The fact that this other person seems to hold so much attraction means that something is missing in your relationship," she said. "The truth is, obligations and time can wear away even the best relationship unless both partners are willing to make the effort to keep it vital. Don't get comfortable. Put that extra effort in, try to look your best for your husband or wife and you'll send a message that what he or she thinks about you really is important."

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If the thought of initiating sex leaves you feeling anxious -- and you've exhausted your list of excuses -- you're probably in a sexless marriage, said Nelson.

"Initiating sex means that at least one of you is taking responsibility for the sex part of your marriage," she said. "Someone needs to take charge of keeping the marriage or relationship spicy -- someone needs to dress up, buy the sex toys or turn on the porn. It’s perfectly fine for one partner to be the driving force if it keeps your sex life alive and moving. But when you both stop trying, it can grind the whole sex machine to a halt."

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Sex isn't just physical when you're in a long-term relationship. It's all tied up in how you and your partner feel about the state of the relationship in general. The ultimate foreplay starts with you making your partner feel wanted by simply showing how much he or she still means to you, said Heitler.

"Emotional loving and sexual loving tend to go hand in hand, each enhancing the other. The more thirsty you are for one, the more likely you are thirsty for the other as well," she said. "To get things started, compliment and appreciate your spouse. Share your time, attention and your curiousity about what the other is doing or thinking about and you'll be on the right track."

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