Snictched?

I knew this guy for 3 yrs & he’s hurt me so much & my dumb ass would forgive him & let him back into my life. But now I felt like I was ready to lose my virginity to him w/o having feelings attached. So me & him decided to do friends with benefits & wouldn’t tell anyone. Until I found out he was dating a girl the entire time & they were going to fuck. After finding that out, I was disgusted with what he was doing & i wanted to tell the other girl (politely) that her bf was cheating on her with me because if I was the girl I would want to know. But I felt like I built my anger of him hurting me so much I kind of wanted to get revenge back at him & put him in his place but again I was fwb with the guy & it was really not my place to say anything especially to her, if it should’ve came from the guy, which I knew he wouldn’t have told her anything. Was it a good idea to snitch?