This won't help your loneliness but I strongly urge you to consult with an attorney about your and your child's rights and doing what is best to protect her. Not putting his name on the birth certificate only makes it more difficult for him to exercise his rights but he still can if he's focused. Sounds like he might not be. Perhaps he's making a threat to have baby live with him to get back at you. I definitely agree that it would be best for him to not have primary or even shared custody with you. At the same time it may be important that your child know his/her father when they are older. While (s)he is a baby, consistency and security are very important and I wouldn't want someone like you describe around.
If you can't afford an attorney, make an appointment with legal aid. You will feel more secure if you're able to get a court order ahead of time. I don't know if that's possible but it's worth asking about. It will definitely be important for you to know what the law is concerning custody so that you can make plans.
I support you not including him in your life. He is not mature enough for the type of relationship you need.
What are your interests? Join a club or group with an interest based focus. It doesn't matter if members are parents or single parents or not.
Another idea is to join Parents Without Partners. We have a very active group in our city. If you read, the library has book clubs. If you garden or are just interested in gardening there are garden clubs. I've been in a couple of Gourmet Dining Clubs and started another one many years ago. I learned about them in the local interest newspaper.
Take a prenatal class. You're apt to meet another single mom there. Be open to being friends with a married mom. Your hospital may have a new mom's support group.
Find a church, if you don't already attend. There you'll meet older women who would like to take you under their wing. And there may be a singles group too.
Look in the phone book, on the web, in the local free newspaper you'll find at grocery stores for a support group. It doesn't have to be one focused on single moms or babies. I've talked with people who went to Alanon even tho they didn't have a drug problem in the family and found good support. Actually, when I think about it, Alanon might be a very good fit for you since your ex smokes pot in excess.
I suspect your family will be more involved once the baby is here. Babies win hearts. Have you reached out to them by including them in plans for the nursery, clothes, learning about pregnancy and parenting? Invite them over for dinner and a movie on the DVD player.
When I was your age and older, I was good friends with a couple of different women who were single mothers. I love kids and loved being involved with their families. I met both of them at work.
Don't move away. You'd have to start everything over and that would be even more of a downer. Can you imagine finding a place to live, where to buy groceries, not knowing the area, etc.?
If you're not working, have you applied for state assistance? Go early for appointments. The waiting room is nearly always full of people. Strike up conversations and see if you run into someone you'll like.
Most important of all is to get started in counseling. You must be depressed and need someone to talk with. Groups run by professional therapists are inexpensive and will not only give you somewhere to talk but will also help you find a way out of depression, give you other ways of looking at things, and in general be supportive. Again, you can find a group in the local social "gab" sheet. Call your county's mental health office and ask about the ones they run. You can get one on one counseling thru the county also.
If you have insurance call several different offices to find a one on one counselor who takes your insurance.
You can do this! I admire your decision to keep the baby. You are on a difficult path but not an impossible one. Keep reaching out to people, on this site, and in person. The more activities you get involved with the more choices of friends you'll have.