I don’t know what to do

My boyfriend and I have a long distance relationship and we haven’t been able to see each other for a month, he doesn’t have his phone rn so I decided to go into his snapchat and do his streaks, while being in there I come across this one girl from his church who he says they hooked up a while ago and that she stalks him, she even follows me on instagram. On their conversation I see him talking to like we would usually talk calling her baby, love etc etc... as I go up in the conversation I found a part where they are sexting reading that pretty much broke my heart because It happened during one of the times I needed him the most and I just found out, I don’t know if I’m exaggerating but it feels like if he had cheated on me pretty much. I texted him he did admit it, he said that she was texting him and he was horny so he went for it because I couldn’t help him since at that time I wasn’t in the position because I had an accident. He begged me to forgive him and I did, because I love him but I don’t know if I made the right choice I don’t wanna be looking stupid, and I know this is gonna change out relationship since there is gonna be no trust pretty much .