SOMEONE SENT ME A VID OF MY BOYFRIEND FUCKING ANOTHER GIRL!!!!

Someone just sent me a video of my boyfriend having sex with another girl... . The person who sent it to me sent it through a fake account on Facebook. I’m pretty sure it happened a while back but looking at makes me sick. I gave myself space from him to think for a while. I know he did nothing wrong but my question is why are their girls reaching to make me feel a certain way??? And What would you do?

Update: Sadly, I found out that he had been cheating on me. He wasn’t smart about it either. He had been making videos with the girl he was cheating on me with. The girl was unaware that we were dating and had found out. When she found out, she went out on a tangent and decided to make a fake account to try and get to me by sending me the video. When I confronted him about it, he had tried to make it seem as if it was an old video. I reached out to the fake account, we exchanged some words (some not very nice) and she had admitted to me that she was the one he had been cheating on me with. When I confronted him about it again, he had turned silent. I left him, and moved in with my mother. I can’t believe something like this had happened to me, because it was something I was least expecting. He really got me thinking he wanted to marry me. Anyways, It has been roughly 5 days without contact. I don’t think I’ll be going back. To this day, the girl is still sending me messages on different accounts, taunting me. He has tried contacting me too, but I’ve changed my number and blocked him on all social media platforms. That goes for her as well. And no, he wasn’t underage in the video, and neither was she. I decided to be a bigger person and move on from the situation, there should to be a need for an explanation, other than he never loved me and probably enjoyed seeing me in pain.