Unexpected Pregnancy

Jo
So my boyfriend and I just found out I'm pregnant. He's been so on and off about this. He's literally bipolar towards it. He already has a daughter. At first he wanted me to abort it. Then he got over that idea. I even told him no to the idea of adoption because I think we can do this. I told him that even if he is not involved that I can do this on my own. He said that we would work through it. The next night he said that it was my fault and I was jealous of what he and his daughters mother had. That I didn't have a child with him. Though baby fever was putting me through a depression, I didn't want a child right now since I can't give someone who deserves the world anything but the bare minimum; but look where I am now. 
I'm pregnant. I told him that I might move back home since that's where my support system is and I don't have any help of support here except him and he's just making the stress of things on my own in my first pregnancy very hard right now. 
I have always been understanding of his feelings and what he may be thinking about, but he doesn't do that for me. And I'm worried that maybe I won't get that support I need throughout our pregnancy. I am 19 and he is 22. I know I'm not being immature about this, but how long do you think he'll need before he starts coming around and showing interest in our child rather than completely ignoring us for his first daughter. I feel like he's choosing kids and I'm afraid he won't come around from this funk until the baby is here. I know he's just scared and overwhelmed, but I am too (Trust me I've had that talk with him many times) and he just keeps changing what he wants out of this. He says he wasn't ready, but neither was I. I just want him to want our baby. I'm scared and worried but super excited. And I want to share that excitement with him. How long do you think it will take him to come around?.. And I know it's not certain he will either. I just need encouragement and positivity.  If you have a personal experience, please share it and how you dealt with it.