That question has a looong answer I am not willing to write. But short answer is (if I am remembering correctly)slut level is tied to the number of passives you have. If you don't unlock passives slut level shouldn't rise. Don't ask me how you can stop unlocking passives. There are hundreds of them and each have different unlocking conditions that you need to carefully avoid fulfilling
Someone correct me if I am remembering things wrong, it has been a while since the last time I played this game.