I'm not an expert but maybe (I hope not) he might be talking to someone else. If he is getting really distant with you, he might be getting closer to someone else. My boyfriend was getting really distant and when we broke up, I found out he was cheating. You should just try and ask him if something is going on and ask how you can help. Sometimes, you have to let people go. Sorry that you are going through this. I hope it gets better.