marriage trouble. help!

so my husband and I have been married for almost 3 years now. we have four children (two from his previous marriage and two of our own) and we've been pretty happy for a while. But for the past maybe 6 months, he's been different. He doesn't spend time with the kids, he won't spend time with me willingly, and when he does it's like he can't stand being around us. every time I ask him what's wrong he just looks at me with this digusted look, shakes his head, and ignores me and doesn't say a word. Then he gets angry over little things, like me asking him to put a movie on for the kids instead of him playing video games. It's gotten to the point where it seems like he doesn't even want me around. And I ask him if i did something wrong and, again, he just ignores me. So then I get irritated at snap at him (which I know I shouldn't) and he looks at me and says "Don't talk to me that way" as if I were his child (13 year age difference). I'm trying to sit and tall with him when we're both free but he just won't respond. it's like talking to a brick wall...i just feel like hiding in a corner and crying. Oh and he won't have sex with me at all. even if I try to initiate it. what do I do????