Tough situation

Just posting because I need somewhere to vent. My SO and I broke up last September and both started seeing other people, we decided to talk and try to work things out in January. We met to talk and one thing lead to another, we had sex and he didn’t pull out in time. However, four days before that I had a hookup and the condom broke. Unfortunately I obviously don’t know who the father is until he’s born and we can do a DNA test. Please no negative comments I know it wasn’t a smart thing to do, but if I would’ve predicted my ex and I at the time would’ve ever decided to meet up and talk again I would’ve never slept with the other guy. Anyway, my SO knows that the baby may not be his, and the other guy also knows that the baby could potentially be his. Since January my SO have been together and things have been amazing, we’re the best we’ve been in the last 6 years we’ve been together. However, he tells me that if the baby is not his he will leave me. I completely understand where he’s coming from, but it also hurts me that our love isn’t enough for him to stay. He’s said over and over he’s with me because he wants to be not because of the baby, so I guess it just hurts that he will leave me if the baby isn’t his.. anyone else go through this?