am i overreacting?

my boyfriend and i have been together two years and i’ve caught him talking to other girls before. he swears up and down it’s never been physical and he says he will never ever do it again. well, just a little bit ago i saw he added a girl on fb…he only had 2 mutual friends w her. her profile pic was her like hunched over and her boobs were like boom right there. when i saw that, it honestly broke my heart because i feel like he saw a post of hers or maybe she was under “people you may know” and he thought she was attractive and added her. i don’t add guys unless i personally know them from a long time ago or family of course. i don’t see the need for him to be adding any girls if he’s in a relationship and doesn’t personally know them. he’s also never mentioned her. i asked him why he added her but he fell asleep and now i’m really overthinking. do you think i’m overreacting or would you be upset too?