ejaculation w/o orgasm, can't feel much

Not me, my partner. Over the last 10+ years he's had less and less feeling in his penis. He can feel pressure, but aside from that there's about a half postage stamp size spot just below the groove in the head of his penis where he can feel 'good friction'. That's diminishing too - the stimulation has to be beyond the level that should be painful. So, he can get it up but can't feel much and when he does climax often can't feel it except muscle spasm and what he describes as "oh, I'm done..." - or - he wears out and gives up -or- he tries for so long that it becomes uncomfortable, then painful, for me. He tried yohimbe but all that did was give him an upset stomach. Oral works a little better because I can target whatever obviously feels good to him, but that still takes him about 40 minutes. 40 minutes leaves me feeling like I've just induced TMJ ( he's large).

The expectation that It Won't Work is contributing to 'it's not working' too. For me, knowing the only thing that will definitely get him off is oral so I *should* blow him has started to feel like an obligation. I ordinarily enjoy sex with him; being aware of and always monitoring how he's doing really really really interferes with that.

He's in his 50s, slightly overweight, chronically moderately depressed, not on meds, horny most of the time and has been putting off talking to a doctor about this for at least 5 years. Other than he ought to see a neurologist, what the heck is this? I don't even have a label for it so I can go googling.

Grax

He needs to start out with a thorough physical.
Don't try diagnosing or self-treatment of this on his own. It may very well be related to circulatory or neural issues. How is his blood pressure and prostate?
The doctor can refer him to a specialist if necessary. Let the experts decide the best course of action.
Best of luck to you both.