Sorry, now who's making assumptions?
Where does op say the sex is painful or uncomfortable?
You say she's responsible for hers and his orgasms - where does she say that he orgasms?
Yes, the medication is prescribed for him but he doesn't take it every time. Presumably that's because he doesn't want to.
Op wants oral sex but he doesn't do it, presumably because he doesn't want to?
So, to get him to take the medication more often, when he doesn't want to, or to get him to take the medication more frequently, when he doesn't want to, is wrong.
She has a right to have a fulfilling sex life.
No one has a right to a sex life. She may want a fulfilling sex life. It might not be possible within this relationship so op should leave if that's what she needs.
She needs to talk to him about it and if he refuses to compromise as she has already been doing for years then yes, I think she should leave him.
What compromise do you want?