boyfriend problems

I could really use some advice.. my boyfriend and I have been together for two years now. I'm 19 weeks pregnant today and last night I had to go looking for him because he was out drinking and doing drugs, we had a promise not to do those things for the safety and wellbeing of the baby. He hardly talks to me about our problems unless he's yelling over text or on the phone and it's like he's given up on our relationship.. I really love him.. so much so that I haven't been able to get the courage to just leave. I have really bad trust issues because of my family in the past. My grandfather has health problems and my brothers suicidal. And everytime I ask him if I can talk to him about it he gets upset.. what can I do without leaving..