Hello, my friend:
What a terrible situation to find yourself in. Based on what I read I think you know what you need to do and are looking for validation from us.
The past two responses (Melissa is a very smart woman, trust me) have validated what you want to do. Do what you have to do legally to get this guy to take his reponsibility for this child. Don't let him slip away as far as this goes.
If he has a "roomie" then I'll bet she's probably on to him by now. I'll bet he's cheated on her several times (if they're still together). She may have even left him by now and he's preying on someone else.
As far as what to do for yourself, you have to take the best care of yourself more now than ever. Eat right, get sleep, take exercise, talk to whomever to help you get past this speed bump. No alcohol, drugs or anything else. Your health and the health of this unborn child are the most important things in your life right now (besides keeping this guy from not doing right by you).
Please, please, please take care of yourself. Just because he did you wrong doesn't mean you should do yourself wrong.
Good luck and please keep posting.