Females, what would you do?

If you found your boyfriend on the *** app (app for gay men) what would you do? Would you tell him? I know he will just deny it even with the truth in front of his face. I’m afraid it would make him defensive. The worst part is if he could be open about it I could find a way to be ok with it. But hiding it and lying pisses me off more then anything. Not to mention he is putting me at a risk without knowing it, which is unfair. What do I do??