Would you be mad or am I crazy!?

So here's my issue me and my SO started dating and hanging out in December of last year, well he left his lap top on and I don't ushually go through his things but something told me to and I found a conversation between him and a girl in another town saying how he wanted to excuse my language but saying " I can't wait to sleep with you again and get your panties all wet like last time..." And ladies it was a lot worse than just this like in detail. But like I said we just started hanging out and dating but it was not 100 percent official. I guess it hurts because I thought I was the only one he was Pershing.... Would you be hurt?