My sex life has gone down hill...no sex in 2 weeks?!

So my boyfriend and I have been together 4 years, and we live together. Our sex life was never amazing, but it would happen at least twice a week. Now it rarely happens... I'm so sexually attracted to him and all I want is to have sex with him but he's never in the mood. It seems like there's nothing I can do. I've tried talking to him and he says it's just pretty much how he is now, he just has a very low sex drive. What should I do? All I want is to have a good sex life with him... it's been 2 weeks so far!