Need Marriage information

[Magnolia]

Hello, hope I won't be judged. I'm sincere in my post so please only sincere answers.
From what I have learned of Islam, I have fallen in love with. I am interested in conversion but am overwhelmed at the thought as there seems to be so much to learn.
I am love with a Muslim man who is very adept at explaining the teachings of Islam. I could listen to him all day talk about it.
Here is where it gets complicated. He says he is under an agreement with his Wife that they are not "together" but they have children and have agreed to raise their children under the same roof. She does come in when we are speaking and he doesn't flinch. He however keeps a closed mouth and I can't pry much info out as he just says it's not an issue because they are not "together."
I told him I don't want to be doing anything like a mistress does and betraying anyone's marriage which I believe is a sin. He assured me he is just as moral and wouldn't betray God or his wife like that.
My first question is..Does this sound like I'm being naive?
It gets more complicated... I am pregnant with his child. He was happy about this and has made an honorable effort to be supportive and he has never made me wonder or doubt that he is happy about fathering this child.
My next question is this..
I want to marry him. I am however divorced with a child already. Is this a problem in Islam?
I have hinted that I would like to marry and that I know I'd be the second wife. I respect him as a father and would never want him to leave his kids. I live him and just want to be married to him and in a decent relationship. Currently this relationship has me feeling like a mistress no matter how much he argues that I am not.
We haven't had a real discussion on marriage. He is devout and I am sure he wouldn't just lightly throw it out there.
He expressed we need to sit down and really talk about our needs in this relationship downs can both be happy. I will be hoping that is the topic he wants to discuss.
I know I sound like an idiot but this is my situation and I hope someone can give me some advice good or bad.. I just need clarity. Please be kind. Thanks

[Umm Abed]

Firstly, welcome to the forum and welcome to Islam. What this man has done is not in accordance with Islam. You are not to be blamed but no devout person would involve himself with another without marriage, and now you'r pregnant. Your being divorced and with a child is no problem in Islam and you are free to marry, but personally I would be very wary of him.

If despite all that he has done and you still want to marry him then do it the right way - tell him you will only be in a relationship if he marries you and you are prepared to learn about Islam and remember, little steps along the way of learning so dont feel overwhelmed.