Advice please?

My boyfriend has given me chlamydia and im 33 weeks pregnan. He was here when I got the results and he was so calm about it. He was comforting me crying. He was 100% sure that he hadn't cheated and that it must have been from before we got back together. (We have only been back together a few months, it is his baby im pregnant with. When I first found out I was pregnant we weren't together and didn't get back together until I was about 16 weeks) I asked him why are u so calm about it, he said because he knows he's done nothing wrong and that it's from before and he can't take it back now. He even swore on our babies life and his grandfather's grave. I have no idea what to do or what to believe. However i honeslty cant think when he could have had the chance to sleep with someone else since we have been together. We have been so happy looking forward to being a family. He said hes sorry and said it should be left in the past and carry on as we were because something that happened before we got together isn't worth losing what we have now. I know you can't tell me if he's telling the truth or not but what you can tell me is what you'd do in my situation. Would you take a huge risk and stay? I need some serious advice I really don't know what to do everything was perfect until now 😢