I need some advice.

So I'm posting anonymously because I'm actually embarrassed.

My boyfriend and I have been together over 3 years now. I've loved him every second, even during the bad times. He's had a rough childhood and started drinking when he was young (15). He had a drinking problem when we first got together and has gotten so much better. He goes to work are rarely drinks during the week. He works mon-thurs and gets paid on Thursday. He often buys a couple cases on Thursday and Friday nights. He says he drinks because he is bored. He will get completely hammered and pass out. I work nights so I get home at 6am and hes passed out with the ashtray on the bed. Its only 6pm on a Friday and he is already passed out on the couch. I ask him if he's going to drink like this when the baby comes and he says no. I'm worried I'm making the wrong decision for me and my baby. I don't have the means to just up and leave and I don't know what to do. :( any thoughts??