My FWB lied about needing protection

I’m processing some feelings so I apologize if this is all over the place.

I dated a guy years ago, but before we became official, i found out he was sleeping with a mutual friend without telling either of us. He justified it by saying we weren’t really “together.” I was young and dumb so i stayed with him for a year, we remained friends after our breakup, and became FWB several years later. I was always really clear that while it wasn’t serious, I required open communication about who else he was seeing because of our past experience. I also wanted to make an informed decision about whether we needed protection. He agreed with all of this and asked for the same in return.

During our last session, a friend of his was blowing up his phone all night. She was going through a separation from her husband and needed help moving. It was over the top, so I asked if they were romantically involved. FWB got defensive and said they’d been friends for years and i was insecure for even asking. It put a damper on the rest of the night. Shortly afterwards, he moved away so we haven’t seen each other since, and it’s been about 5 years.

I’m on a kink site, and I must’ve friended FWB on it a long time ago. Last night he came up in my feed, so i checked his page out of curiosity. He’s now living with the divorced friend–the gut don’t lie, so no surprise there. I scrolled through the photos, and my stomach dropped. There were pictures of her with him dating back before our last session. They’d been sexually active for at least three months at the time i asked about her. There were pictures of them together on the same night we last met, and photos of him with third woman. So not only was he lying about the divorced friend, but he was sleeping with another person that I’ve never heard of. They weren’t using protection in any of the ohotos. Based on his assurances that he wasn’t active with anyone else, neither did we.

I’ve barely thought about this guy in years, but now can’t stop thinking about this. I’m retroactively mad that he lied to my face. I feel betrayed and used, like he knew the risk and still chose to not use a condom. He straight-faced said I was insecure and crazy to suggest he was sleeping with someone he was actually sleeping with! All my STI tests have been negative, but I’m furious that he put me at risk and didn’t give me the information I needed to make that decision myself. And I have to process all this hurt silently because it happened like 5 years ago, so its not like i can just call him up and yell at him. I just had to get this off my chest.