I think the answer is yes but he has planted doubt in my mind. This is the story...

A couple days ago I was using kindle on his phone to read since our kids had my phone. At 11pm I saw a msg that said "breakfast lol" on messenger & became intrigued. It was not my intention to read the msg. I thought that clicking her photo would lead to her fb page but it opened the msgs & although I didn't see anything out the way crazy crazy, I still could see that something was going on with this girl. So I went to check his phone msgs & saw more things that I felt confirmed my suspicions. The main one that got me was him saying "i'm coming to you. I need it 😍" He has no explanation for why he said that or the context behind it.

He has completely denied & is saying these like why would I mess up my 5yr relationship? Why have kids together? Why ask you to marry me? And I'm wondering the same thing. I have no idea what to do. I do not believe him and I have told him this numerous times. But that little trickle of doubt... what if I leave and he really wasn't cheating? Idk

It looks bad though right? Because I don't think I'm tripping and I'm ready to break it off right now