I don't think we've had the pleasure of meeting. Welcome to the Board. I am a neighbor of yours from the Merrimack Valley, and it pains me to see you suffering like this on Thanksgiving. But you've done the right thing by reaching out. So, here's my take for what it's worth.
He is not two months "sober". He has abstained from using for two months There is a difference. Sobriety and recovery is much more than not using. It's about the acceptance of responsibility and being accountable, first to themselves, and then to those who love them. From what you describe, this man is decidedly not sober.
As for the other girl, it's important you understand that sick attracts sick. And if she were truly in recovery, she wouldn't put herself into a situation where she's involved with another woman's man. It reflects that her boundaries are quite permeable. And that's the thing with addicts; their boundaries totally suck. They totally give themselves permission to do things healthy people wouldn't do.
So, what to do? Normally, I don't like to give that sort of advice, but in situations like yours, I make an exception.
Ditch him. Dump him. Lose him. Be f*cking done with him. Now. He has impregnated another woman in the past. He is probably doing something inappropriate with this other chick. You have a daughter that needs a responsible parent. You are in nursing school in order to better yourself. And life is simply too short to be brought down by people whose only concern is the stimulation of the pleasure centers in their brains, whether it's by using opiates or banging people other than their significant others.
Believe it or not, dumping his arse could actually be considered an act of kindness, because you'd be showing him that actions have consequences.
I encourage you to stick around here for support. I also encourage you to check out an Al Anon meeting within the Boston area. There are a ton of them, and I think in-person support would be a big help to you right now.
Anyways, I'm sorry that you have to go through this. But I hope you take comfort in the fact that we have a lot of women here at FFSA who've been in situations similar to yours and lived to tell the tale. You will, too, even if it doesn't feel that way at the moment.
Keep us posted, and again, Welcome to the Board.