You’re right to be worried. Your boyfriend is feeling trapped by the pregnancy and is retreating. 😕
Unfortunately, he has to work through his own issues about his becoming a father and his now life long relationship with you. While he may have been gung ho about getting married before you got pregnant, he never proposed, so it may have been more talk than walk. Now that you’re pregnant, and you’re going to be parents, he’s probably feeling put on the spot, to say the least. All you can do is be there, be supportive, and try and coax him out of his retreat — but it may not work. Try not to blame him or make him feel defensive. Instead, muster up as much understanding and patience as you can.
At the same time you’re trying to be supportive of his emotional crisis, you need to be nurturing of yourself as a new mother. If he’s not going to be there for you, you have to find a support system that includes family and friends so that your pregnancy is a healthy one, and that you weather this relationship problem as best you can.