How to boost drive?

Okay my b/f have been together for almost 2 years and have lived together for over a year. Things ually wise were great when we first met (as usually goes) and now they have just about fizzled out, for him anyways. I know when we first met he was laid off but even when he went back to work things were still HOT but not as HOT as before. But now since he went back to work again from being laid off (happens every winter) things went from HOT to cold. . I know we have both gained some weight since we first met but his "tiredness" and lack of enthusiasm about is well quiet pathetic. Nothing ually intrests him. In fact I think sometimes it bothers him more then excites him (like when I whisper dirty things into his ear when we are in the store or at home). I don't know what to do and everytime I did bring it up he shrugs it off lke "oh well" or acts like a hurt puppy dog and lowers his head. This makes me feel bad for bringing it up. What can I do?!?!!? Seriously, I don't want to be like "put out or I will go somewhere else cause i love him and I know that will hurt more then help. I am in desperate need of help with this.