I have a boyfriend situation. What should I do?

My boyfriend went away for the whole summer, and I hear a rumor that he had a "thing" with a girl at camp. I'm not sure what I should do, like if I should casually ask him if he did anything, or just not ask him about it. I really need some answers because I don't know if I can trust him with even the slight possibility that he did something. But I would also feel terrible if I broke up with him whn he didn't actually do anything because he's a really good guy. What should I do?