I had sex with my best friends girlfriend

My best friend of 15+ years has been with this girl for about 4 years now. I've been having sex with her for the past couple months. He works later than me so we have about 2 hours in the evenings to ourselves. This is not my first time to do this. When I was in HS I used to have sex with another friend of Mines gf that was living with him. I would pass out on the couch and they would go to their bedroom. She would sneak into the living room with me after he went to sleep. We did everything but anal right there in his living room. I never pulled out of her, she always begged me to cum in her and said if she got pregnant she would tell him it's his. I was young and dumb and believed her so I went with it. Luckily I never knocked her up. She was probably a 6 but had a cute little body and was a real freak and apparently he didn't know lol. She frequently talked about leaving him for me but I always steered away from that. That's been 12 years ago or more and I still think about how hot it was fucking her on the floor risking getting caught. I have some wild details about her if anyone cares to hear let me know.