Feeling alone.

My husband and I (I think) are in a weird rut. We've been together for almost 4 years and our sex life was great in the beginning but has significantly fallen off soon after the honeymoon phase wore off. I've gained about 25lb since we first started dating, no children, no extra stress....just the "contented cow syndrome". I ask him if there's something wrong probably more often than I should and he gets really frustrated and angry at me. He's incredibly cuddly and shows A LOT of affection...but our sex life sucks. Like we're just not on the same page. I've never been the type to initiate sex. Ever. But I've also never had to "ask" for it either. I just don't know how to go about initiating. It probably sounds pathetic. Hahaha I asked him tonight if there was anything wrong with me and it was the same old song and dance. I ask, he gets mad, I end up in tears. I feel like he's gotten bored. I just don't know how to fix it.

Has anyone felt like this before? What did you do? Keep in mind I'm a very timid person and really don't know if being the aggressor is something I can do.... or even know how to go about doing.

Anyone out there? :/