Should I break up with him or ask I overreacting?

I went to use my boyfriend phone to find my phone. I accidentally hit a text and it says I want to suck your dick so bad. His reply was hadkle. Who knows what that means. He's trying to say somebody used his phone and he had no idea. But she tried to send pictures and he told her to send them to her Google voice which I recognized. He acted like I'm overreacting and that it hurts that I would think that he could cheat... I don't know what to think. I love him more than anyone ever. He is so good with my son. I've never loved anyone so much, which makes it hurt so much more. We were trying to have a baby and still swears I'm the only one and he wants only me. I've never felt so conflicted. I'm 30 and have never hurt so bad.. what are your opinions?