Don't, don't, don't.
Stick to the porn version of that fantasy.
The guy is a doctor, not a porn actor. His job is to look after your health, not get you off.
Don't even try it. If you do and he's straight, you lose a doctor. And YOUR medical record will likely have a bonus note like "Warning, acts inappropriately with the doctor."
If you do and he's gay, he won't want to be near you as that can mean losing his license that's he has spent YEARS getting and hundreds of thousands on his schooling. He won't appreciate it.
Yes, there are doctors who are gay out there. That doesn't mean one who's open to being hit on by actual patients.
Instead, try to find someone who wants to PLAY "doctor" with you, there will be much fewer problems all around. And you can keep reimagining the "Oh my, this doctor just hit on me out of the blue!" scenario time and time again, which wouldn't happen more than once in real life, if ever.
I was married to a nurse for ~20 years, he told tales of NURSES acting inappropriately with patients and the amount of legal and professional shit they got into for getting into that sort of activity is massive. Lost jobs, lost careers, lost homes... Don't do that to your doc.
Set up a fantasy with a buddy. But that's as far as you should go.