My husband and I have been married for 30 years and sex for us involves me using my finger to do myself. He just isn't great at knowing how to get me there.
I remember one encounter years ago where we just laid side by side doing ourselves. Maybe I'm weird, but it was a real turn on for me. He felt awkward masturbating in front of me which made me appreciate his willingness to be open with me.
Maybe you could start by letting him watch you masturbate without having sex after. If the room were dark or he were just peeking around the corner?
I don't know. I hope you can find a way. It's worth fighting for.