BOY TROUBLES

I need your girls advice.. my boyfriend and i are 17 and have been dating for 23 months and the the other day i was checking his phone and saw messages to another girl saying that he is loosing feelings and he was thinking about breaking up with me after our presentation ball. I confronted him not long after and he said he didn’t mean it and he just has a lot going on at the moment and he didn’t think he would make it to deb and he wanted to make it past then. He is suffering mentally like really bad. I don’t know what to do