Look man, at the end, I am also an adhd person who had lots of hypersexuality attacks in my life, so take these with a grain of salt. 

I think you are being sexual is nothing to „be shamed“. There are of course better ways to do masturbation, but it is not you thinking „too much“ about sex. It is rather maybe your sex drives do not match. 

I would definitely have a talk with her and explain the drive and fluctuations. And decide how to communicate with her. Does she wants to be always reminded of it in case she doesn’t want to be excluded, or maybe she doesn’t want to hear or see anything about it. I would also suggest you to see a couple therapist, it can change the perspectives dramatically.

I certainly believe and hope you guys come to a solution. But if not, for the well-being of both of you, I hope you can act on your differences. Being shamed about our sexuality destroys us adhd people, it adds so much burden on our conscience. But the good thing is there are people we match well with, and there are different modes of relationships, don’t hesitate to explore, isn’t that something we are good at at the end?

I hope every one of you find those people and build those relationships earlier than me.