Why does this happen...

I just found out my boyfriend has been flirting and getting sexual with his female hairdresser. He accidentally sent me a Snapchat meant for his guy friends of her boobs pressed up against his face while she was waxing his eyebrows.. to my understanding he hasn’t done more than that and endless flirting with her when he visits every 2 weeks....

What should I do... I’m so fucking crushed right now..

Update: When I confronted him about it, all he said was “damn I should have double checked before I sent it.”

What the fuck