Micro cheating.

I 21f recently had a feeling to check my 21M bfs phone, upon going through it I seen he was texting with another guy months back at the beginning of our relationship. He didn’t do anything with this guy but said guy talked about how much he wanted to suck my bf off and my bf didn’t tell him not to talk like that, he did mention he was straight and had a gf so he “wasn’t sure”. Idek what to do with this information…how do I even bring this upto him in the morning? I honestly never thought I’d be out in this situation again. My nervous system is going haywire because he’s all I have….what do I do????