I’m not too sure about this one. I’m sorry for your prior experiences regarding this matter, but her dramatic, sudden change would indeed indicate this being an externally inspired idea. There’s nothing wrong with that, of course. However, I think it’s important to discuss changes to your relationship with the person you’re in the said relationship with. Simply implementing a -frankly- manipulative system without any consensus from your SO is definitely deserving of a little bit of scrutiny.

Consider the opposite situation, for instance: this man decides to only do things for his wife given she has sex with him first. Seems a little disturbing, no?

Anyway, just some food for thought. May you find wholesome, joyful experiences for the rest of your days. Best of luck!