Pregnant and he won't commit. Why?

So I've been in a relationship with this guy for over a year now. Our relationship has always been a little rocky, but when we recently found out that I was pregnant things began to look up. The relationship got better and we worked out our problems, but that only lasted a short while. We don't live together and since my emotions are a wreck lately I tend to take things the wrong way and when he disappears I accuse him of cheating. Is he? I don't know... I know I shouldn't accuse with out proof but the last time I accused him it turned into a blow out fight. He said we would talk about things but that hasn't happened and every time I try to explain my feelings he blows me off. For the past week he won't talk to me more than 5 minutes at a time and this whole weekend he hasn't answered the phone until 4 am and he's playing the disappearing game. Now he won't answer at all. I guess what I'm getting at is asking if I've driven him away or if he just isn't ready for commitment... I know I didn't explain this perfectly so any questions feel free to ask.
Pregnant and he won't commit. Why?
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