What do I do?

So my boyfriend of 2 years openly confessed to me last night that a random girl added him on Snapchat and he added her back. She then asked him to go onto Google hangouts and video call. So he did. He then got very upset and cried when he admitted to me that she was fully naked in the video call and he was masterbating. It hurts me so much to think that he was naked over a video call with another female. He’s never been like this. And I can tell he’s so sorry. He’s never cried since I’ve known him and he hasn’t stopped crying for about 3 days now. I want to stay with him. But I am so hurt. I just need some advice on what you guys would do in my situation. And why you’d decide on that. Thankyou