I slept with my ex

My bf and I have been together for 5 months now. We have a mediocre sex life. I’m a bit of a nymphomaniac. I’ve communicated to him what I like and he says he doesn’t want to. I’ve been friends with my ex longer than the 5 months. So one day we were hanging out and we slept together, like multiple times. My bf and I have discussed an open relationship so I can explore more of my sexuality, bdsm, hardcore....and he’s agreed to let me do this. We have also promised that no matter who we sleep with, we’ll always be together. I have no romantic feelings for my ex and we’ve made it clear that we are just friends. I have deep feelings for my boyfriend and he was there when I was recovering from a date rape.