What should I do?

So I went to England and Paris for ten days with my school group and in my school group there were a bunch of my friends. There was also my ex boyfriend. Me and him never talked until this event but during this we were placed as safety partners for the ten days so this means we went every where together the only thing we didn’t do is share a hotel bed room. But he would come over to my room just so we can talk. But the last night in Paris we ended up having sex. (It was the best sex I’ve ever had) but I had no intention of getting back together with him and then that happen. My question is. Am I obligated to give him another chance now that we had sex or no? I’m also leaving for 2 months to go out of state again, so should I wait till I come back to get with him? I’m so lost and confused. plz help