I am giong thru a similar situation. My fiance and I are in the same boat... Having a lot of sex, then none for a few weeks. I think it's a combination of a couple things...
1. Being stressed. I KNOW this is the major factor in our sex life. With wedding planning, and other personal things going on in our life right now, we're just too stressed, so it kind of kills the romance factor.
2. is the fact that we are sooo busy! Again, the wedding planning, work, the gym, cooking, cleaning, taking care of our pets leaves little time for 'us'.
3. Hey the rabbit sex will stop at some point. We were the same way when we started dating over 4 1/2 years ago. I think that always changes in relationships after years. Try to spice it up a little. Buy toys, pornos, dress up, whatever you're into. Try new things!
It may not go right back to the way it used to be when you first started dating, but take some time out at least a couple times a week for you two. Try different things and make it happen even if you're not in the mood. Sometimes I'm nowhere near being in the mood, but we'll put a "movie" in and start doing things and then I'll be totally into it. Also maybe even if you're not in the mood, put out for him anyway. I don't mean to sound rude, but I do that a lot. I know men have their "needs" when it comes to sex, and they need it a lot more than we do. Let him "poke" you in the shower (sorry, that's what we call it. haha). Hopefully that helps you a little. I'm sorry you're going thru this, but i definitely understand.