How Did We Get To This Point?

When my husband and I first got together we laughed, shared the same taste in music and movies, talked about everything, respected each others opinions and in general we were best friends. But over the last two years all of that has faded away and we almost never talk and when we do it usually ends up in an argument or one of us being annoyed, he talks down to me like I'm a complete moron and is only nice to me when he wants to have sex. (Sorry but it's the truth)
He uses me as an excuse for everything he does. He drinks more now (and other things) because he's trying to be a little happy. He is negative and moody because I pay too much attention to him (or I'm ignoring him, whichever scenario fits at that moment) I'm too sensitive to all of the things he says and I need let things go, like him telling me to shut up or that he is over this and he is done.
I know I am not perfect but at this point I have succumbed to almost complete numbness and only speak to him on an as needed basis. I just don't understand how we got here..and am I really too sensitive, do other people just deal with this stuff and start fresh the next day?
I honestly have no idea and I don't want to start over again. But I don't know how to fix things or at this point who needs to fix what.
It's so confusing and such a shame to see something that could be so great be the source of all of my unhappiness.