My current bf was in a relationship when we first started talking

So me and my current bf met on a dating app. So he was already in a relationship when we started talking and i didn’t know this until 3-4 months into the talking phase. He told me that there was no chemistry and that he didn’t feel like he was in a relationship because the girl didn’t really care that much about him like they rarely talked and stuff. He broke up with her after and i was already too in love with him to leave him. So i decided to forgive him and now we’re together. But i still keep thinking about it and feel guilty. Im scared that he’ll betray me asw