Advise?! Sorry too long

I'm looking for some advise. Would greatly appreciate it that I'm not judge. I know it's wrong but I just need advise.
I'm currently 15 weeks pregnant by a married military man. I've known him since 2011, we dated then and then I left him thinking I was going to make life with my first child's father. Of course that didn't happen. So he's been married for year. We've always had a contact somehow. We've always had love for each other and still do, well I do. He's separated from his wife and we hooked up. Well I ended up pregnant. I HAD THE PARAGUARD IUD for only 5 years. I wasn't suppose to get pregnant. I know not having sex would of helped but yeah. Well I informed him and he said he would take care of his responsibilities but sometimes he's just so careless. I completely understand that I messed up and it's something that I have to deal with. One day he's so caring and we are picking names out and talking about the baby and some days I'm just completely ignored. He said to let him know what I need and he would help me. I'm going to try to coparent with him. I hate going to court! He has another child already, not with his wife but before her. He's a great father. But if he doesn't help I'm taking him to court for child support. I think my child will benefit more that way. Idk. I'm so confused! Am I over reacting?!? Am I doing the right thing?! Any help???
**No his wife is not aware. And no we are not in a relationship!