Engaged Ex Girlfriend

I got my first real girlfriend when I was 21 and she was 17. She is easily the most beautiful girl I have ever been with, way above my level. We only lasted one year, unfortunately. I met her again this summer. She is already a chemist, I am a teacher and a serious underachiever. Turned out she was engaged. We decided to have lunch and catch up. We then took a short hike, and she decided she wanted to show me her and her fiance's new apartment, which was just nearby. I have no idea how it happened, but 20 minutes later I was balls deep in her pussy, taking her from behind as she was screaming my name as I had never heard her scream before. After I finished inside her, I thought it would be akward, with her just having cheated and all, but we ended up laying in bed and cuddling, just like in old times. She told me her fiance was away for the weekend for a business trip and asked if I wanted to keep her company for the duration, I eagerly accepted. We ordered take away food, watch some movies, had some wine, took a stroll in the park. Oh, and we fucked and sucked each other silly. The first evening, she let me cum on her engagement ring and her chest before she called her fiance. With my cum all over her and while toying with my dick and balls, she told him how she had met her "loser ex boyfriend" earlier that day. The next evening, her fiance called her during our foreplay. She talked with him while sitting on my legs and playing with my dick. She then took my cock inside her pussy, told him she loved him, hung up and proceeded to ride me until we both came. She was never so naughty or slutty while I was with her. This makes me happy that we did not become a permanent thing and even happier that we met again. She texted me a few days ago, asking me if she could come over this weekend. I had to cancel a night out with some friends, but I of course said yes!