The pain aspect is something you should address. First with your partner if their technique can be changed, and second with a few doctors. This one is like a layer cake - maybe you’re ace, maybe there is emotional context (that could be entirely unrelated to your current situation) that causes physical discomfort, or possibly there’s a physical component that your doctor might be able to help you with. Or some combination of all of them, because people are complex.
But romantic asexuality is definitely a thing, as is a number of variants within it.

Being treated only as a font of knowledge, a hard worker, a reliable friend (when the friendship is otherwise not rewarding), having a lot of tools, etc, is kind of crappy. I at least get pleasure from sex. Honestly, if I had my druthers of how folks reduce me, I wouldn’t hate being valued for being good in bed.
I wonder if the friend with the truck ever feels like that.