College relationships

My boyfriend is going to college and I'm going to be a senior in high school. I trust him 100% but when we had the talk about him partying and not cheating on me he acted super weird. I said "please don't cheat on me because that would hurt more than anything blah blah blah.." But his response was only, "done worry I'll be fine". It was weird because I sent a nice long text about my feelings. Should I be worried? What should I say to make sure our relationship doesn't get messed up??