I recently found out that my boyfriend is married, they filed for separation... but part of me feels like he's lying to me because I have never seen the papers. He recently had a baby with this woman, I found out about the marriage and the child when I was already a few months pregnant. He left her a year ago but they're still married, I'm terrified he's going to leave me for his wife, he's been living with me for about 8 months or more... but I can't stop nagging him about his past, I don't know how to get over all this, I feel lied to and betrayed as well as ashamed, nobody in my family knows because I'm too ashamed to tell them about his children. I feel I should try to work things out with him because he has made it clear to his wife that he doesn't want to be with her, I have even met his children... But it kills me they're still married. Part of the reason I stayed is because his family swears it was a forced marriage and they were just being "young and stupid"... I don't know if I should leave. I love him, but I don't know if I can't get over this.

Young and stupid for how long exactly? How many kids do they have together? And how far away are they?
I'm not quite buying that story from his family.
If he were just your boyfriend with no baby on the way, I would say it's none of your business. But with a baby, it is your business. You ask for answers and proof and if you don't get them, you walk. Nagging will just drive him away first. Be calm, firm, and mean what you say about leaving, and have a plan. It will hurt horribly at first but it's better than losing every ounce of integrity. You even have more options now about the baby, like adoption. I'm not suggesting that, just saying that the sooner this is resolved the better.

They have been married for 3 years now, and have been separated for a year and half, even she admits to being separated for that long... She claims to want the divorce too but either of them are doing anything to get things movinG, I think partly because either have the money to afford the divorce... I don't know if I should believe them, a few weeks ago she was still saying she still in love with him... Part of me feels horrible, like a "homewrecker"... but I had no idea about his children, he kept them a secret from me because he said he knew I wouldn't stay if I knew about it... when I found out I was pregnant his wife was 9 months... I don't understand y his family never said anything to me, no one did,. I want to leave, but he tries hard, and treats me good, its just these lies that are making it hard to stay, I'm constantly wondering what else he's lying about. I have never thought about adoption, and don't really think its an option... I just never thought I'd be in this situation, and never thought I'd be considering being a single mother. I'm terrified of the thought, and ashamed of anyone finding out my relationship I'm in.

... have been separated for a year and half,. his wife was 9 months...

You've been with him 8-9 months... are say 4 months pregnant? His wife had a baby around the time you got pregnant, so she had sex with him 12-13 months ago! Just a few months before you met. So I'm not getting this year to year and a half separated. DO THE MATH!

Get the idea that you are a homewrecker out of your head. HE'S just wrecked the lives of TWO women, both with infants just born or on the way.

So once you get rid of that non-guilt, you can start working on the lies vs 'treating you good.' He let you get pregnant knowing full well that he not only had kids (you still haven't said how many) but also one a newborn. Lies and deceit, no matter how much he thought you'd leave him if you knew, is NOT a good man. It's selfish! He can appear like he's 'trying' all he wants but it's all for him, nobody else.

Yeah I realize they were sleeping together a while ago, but were still separated, not living together or anything, even living in different towns hours away from each other... I found out about the pregnancy when she was 7 months, and the marriage shortly after I was already 2 or 3 months pregnant, I got pregnant within a short time of us being together, he's made it clear to her that he wants nothing to do with her except when it comes to his kids, he has supported me and stood by me through all of this, I just hope this isn't temporary, because now I have this child permanently... I guess I'm just venting right now, this is the first time I have mentioned anything about this, thank you for your advice, I'm trying to come to terms with the predicament I have gotten myself into, and have been allowing myself to be in... :/

OK, I just feel that my job is to see him as a selfish liar. Which I do, and it's not out of thin air either - most of it is taken from how you write about it.
You will make your choices, and as a total stranger, that's all the same to me or anyone here. Family and friends take it personally sometimes.
So feel free to vent all you want, and wait for others to weigh in.
But without sounding like a broken record, do you hear what you just said, really a repeat of what you have been saying in so many words?
'He has supported you and stood by you through all this!! '
WHAT? He's the CAUSE of 'all this!! '
If he had told you the truth you would have made other choices!

I am glad she cleared up it is OK for him to sleep with other women as long as they just have sex and don't live together.

And yes if you are always nagging and complaining about his past he will leave you very soon.