Help please

Sarah
So I came home from work one morning to see my boyfriend of 10 years complaining about his stomach hurting so I lay down next to him and he smells like alcohol so he end up telling me that him and his friends were doing body shots so I got mad that his friends were egging him to do it that it wasn't that type of body shots and that it didn't mean anything but later the same day I notice a Hickey I don't know what to do I need HELP I would never do that to him throughout the 10 years I never let another man ever get that close to me ever I've talked to my best friend and she feels like something more happened that he cheated on me....I'm I overreacting i don't know what to do