Wow this is a tough one, have you been going out for very long? Have you always felt this way about sex? I personally love sex, mind you I no longer think about it as much as I did when I was 20, but still it is one of the great joys of life.
One way to spruce up your sex life is to do something you have never done before. For example, if you never bathe or shower with your partner, you can try that. Sex in the shower can be amazing!
Or if you always have sex at the same time in the day or in the same place, try somewhere different. Try doing it in the kitchen for instance in the morning. Spontaneity and unpredictability is very helpful for a good sex life.
Finally, and I hate to bring this up, you may want to honestly examine your feelings for your bf. I find that if the feelings are not strong enough then they will eventually impact on the sex.
Best of luck.