My EX Wife is pregnant?

My EX Wife Alycia called me yesterday and told me she was pregnant. I wished her congratulations and the best. She told me that the baby was possibly mine. I asked her what she was talking and she reminded me months ago we we met to discuss alimony and we started reminiscing about old times and i mentioned how i wish we had a child together because i know she would be a great mother. She told me it is still possible. She started stripping and kissing me and one thing lead to another and we made love. I was drinking that night but i don't think i was drunk. She told me i was the only person she has had unprotected with so the baby has to be mine. I'm confused happy and angry. I want to be a father and am happy she is going to be a mom but we still argue and haven't resolved our issues that ended our marriage. I think i used a condom but i can't remember. I also still care about her and possibly still love her. However i don't want our child growing up in a hostile environment. What should i do if the baby is mine?