Sex isn't everything in a relationship, but when it's missing, everything else just doesn't seem quite right.
At 27, your guy's sex drive should still be near its peak, not dwindling off to nothing. And if you're like most women, your sex drive will increase in the years to come. If you don't want to be a frustrated wife in a sexless marriage, I advise you get to the bottom of this before getting married.
Don't blame yourself, thinking that you "don't attract him." If you're interested in sex and show it, a 27-year-old man in love should be hot for you day and night -- whether your hair's in curlers, or you're in your ratty jeans, or if you're sound asleep in the morning.
Sure, men vary in their sex drive. But young men's horniness is biological and near-universal. If it's virtually absent, something's wrong. It could be that he's getting sex elsewhere; be alert for this possibility.
Or he could have a pyschological problem. Try to narrow down on the situation. For example, is he having trouble getting an erection? Talk to him about your desires -- not when you're in bed, all expectant, when he may react defensively, but outside of the bedroom. Is something bothering him emotionally or at work? Is he worried about satisfying you? Ask about his desires -- does he want you to do something special to arouse him?
While we all would like sex to be spontaneous, it's healthy to talk about it, too. Try making a "date" for sex, agreeing on a time when you'll unplug the phone and turn off the TV and just be with each other. Spice up your "date" by going shopping together for an erotic video to watch (let him pick it), or read "The Joy of Sex," by Alex Comfort, in bed together.
If doing all this doesn't restore a normal, active sex life, please get help from a therapist or couselor.