Hi Pugs, sounds very muck like your doctor lover needs a doctor, you know what they say, doctors are there worst patients going, there the ones who think its not them, but this time it is.
The problem with ED it can be a sing of other things going wrong, and not just his penis, the best thing for you is drag him along to a good doctor.
Get him tested out, full works.
Good Luck
I don't think age 57 means the end of erections. Your doc has an issue, either from being under a lot of stress (like Life360 suggests) or because he has the kind of problem that something like Viagra is designed to address. It's interesting to me that even with oral, he is beginning to flag. Ask him in the kindest way if he has ever been checked about this, and see what he says.
I think in some ways doctors are under a lot of stress and having vaginal intercourse entails much more effort then laying back with oral. Maybe if you guys went on a vacation where he had more strengh it would be different.
Well not too sure on this age difference thing, but that is for another time. As far as him, HE needs to take care of it. He is a Dr and needs to consult another Dr for his ED.