I need advice

So basically me (19) and my so (20) have been together going on 5 years, except at the end of February we broke up but were still talking. We had plans to move out of state a week after our break up so he left and i stayed. I ended up getting arrested like two days before our leave date then couldnt move until i finished up all my court stuff. We were together after i got out and planned my trip. Fast forward alot to may 14th was the day i got my flight scheduled then i got here may 19th. Around a week ago i found a screenshot my man sent a friend if his, it was a convo between my man and my bestfriend about them wanting to hook up dated on may 14th. 😱 my best fucking friend and my man. They both said they xid it to get back at me. My ex best friend because a guy she was into had feelings for me even tho i was uninterested and he knew that. And my man because we had broken up. So i say whatever try to move on and start fresh but then here i am a week or maybe a little longer later finding out that it was alot more recent than i thought and we were together and im so hurt. 😞 and theres so much history there good and bad im starting to feel like the bad outways the good. But am i strong enough to leave probably not. He makes me look and feel like a fucking idiot but for some reason im obsessed with lobing him it might be how long weve been together idk fuuuuck.