I agree with Chuck.
There has to be more in a relationship than the physical, but that has to be a part of it, too. I dated a girl once when I was in the military and worked odd hours, so whenever we got the chance to get together it was almost always for sex. I told her how I felt and we tried to tone it down a bit, but then I realized that for me there wasn't much more to it than that. Okay, so that was one episode in my life.
Years later I got involved with a woman who was married--although in the process of splitting from her husband--and things worked out kind of similarly in the beginning and the majority of our stolen alone-moments ended up with sex, but I didn't make the same mistake as the previous time. This woman and I would spend evenings together--with friends and her kids--we just couldn't let everyone know about our relationship for a while...but at least we had that time together that wasn't just sex.
There's absolutely nothing wrong with frequent sex, but you yourself have already realized that can't be all there is to it. My suggestion--like many of the others--is to plan ways to spend your days BEFORE sex: hikes and movies, as were suggested, romantic dinners out, long walks holding hands....hell, find an art show or anything to do that will capture your mutual interests for a while. Basically, do things to exercise your minds as well as your glands...but be VERY careful in how you arrange these things because you don't want to give her the idea you don't WANT to have sex! Oh, and one last thing: be sure to give her a little something on these "dates" that will spark her mood and desire...flowers bought from a street vendor...or even purchased ahead of time and waiting for her...and I've found if you spend a little time in a store and find a mushy card that kind of tells her how you feel (one of the long-winded kind, usually) the couple dollars you spend will come back to you in ways you can't possibly imagine.
Best of luck!