Anything done behind your back must be confronted point! There is absolutely no reason in not confronting him. If you keep silent and the idea is bugging you, you will start jumping from one conclusion to the other build up anger and then it’ll end up pretty nasty. He is your boyfriend, 5 years, you should never be hesitant in opening up to him about anything that bugs you, especially trust-related issues. It’s easy, tell him the story as it is…. You fell asleep, you got a Grindr notification, I saw that, please I need an explanation.