Baby daddy drama

My boyfriend of five years (off and on) found out in June that I was pregnant. At the end of May we had a fight and I slept with another guy, but on June 10th I had a positive pregancy test. The entire time my bf had been by my side and he knew about the slip up that happen led but like I said before we already thought I was pregnant. His mom pressured us into getting a prenatal DNA paternity test done and the results came back saying it wasn't my bf's. I am completely devastated and I know he is too. We were so excited and now I can't help but to be sad and think this is all a mistake. After being broken up for a week my ex says that even know my baby isn't his he still wants to go do the dr appointment with me that's coming up. Is this a good idea or just false hope? Should him and I try and make it still work even though the baby isn't his? I need advice