Good heavens, you seem all over the place. First, you write this.
Messages I found on his phone from them too pretty much said he was coming over there but he'd have to wait u too I was asleep
But then you write that it couldn't have happened (even though HE typed out the message on his phone) because you are a light sleeper.
Then you write that she texted you and said she kept her secrets to herself, yet told you they had slept together 2 years ago. Wasn't that a secret?
I don't know if he has cheated on you or not. What I do know is that for some reason, you no longer trust him and believe he might possibly, maybe have cheated on you. Without trust, there is no relationship, so I think you should cut your losses and end it. Not because of anything he "might" have done, but because you have trust issues with him.