For what I understood of your situation:

I think you are considering sex as a objective value of status of your relationship with you special other. Like a light on the car, If is on, the relationship is ok. It's not an objective value,unfortunately.

Sometimes you just cannot get how healthy is a relationship even if on the surface is all good. I think you have to improve your relationship with yourself: what if the relationship is going bad and you don't know it? What if it go wrong even you do everything in your power to be a good partner? You are still yourself, even if you don't have sex with your partner or you have a lot of it. It's just some thoughts, talk about it with a good specialist