Being a pansexual nympho in a monogamous relationship with a man.

This is an actual struggle sometimes. I would love to have someone I could hook up with on occasion because my boyfriend has low testosterone and it's a little frustrating to get turned down sometimes. He says it's okay for me to be with girls on the side, but I guess when it comes to actually doing it, it'd make me feel bad. I mean, I've done things with another girl in his presence, but that's it. Idk what I should do. If anything.