Dear ferretman,
I wish I could wave my magic penis-wand and make it all better! Alas, all I can do is give you some advice. In any event, you know that there are some things you can change and some you can't. Age, for instance. With age, your penis will lose sensation. For some, it's imperceptible; for others, it's very annoying. And yes, for some, circumcision has played a part in desensitizing of the glans penis, although I wouldn't say that this is a given for every circumcized man out there. So what to do:
Well, do as much uncovered as your risk tolerance can stand. No, I don't mean have intercourse without a condom..but maybe handjobs? Advising someone to get BBBJs is controversial, but if you're OK with it...then it may work for you. And of course, if we're talking about a verifiably monogamous partner, e.g your SO/wife/girlfriend or someone you absolutely know is doing it only with you, then skip the condoms altogether and do EVERYTHING bareback.
Whatever you do, use lots of lube so that things don't chafe and make it worse. As to condoms, try the thinner version. If you're not huge down there, polyurethane can work better in the sensation department than latex. But beware - a big penis can break them. If it feels tight and uncomfortable, go back to a generous size latex. Actually, that can also be the problem - a condom that's too small and constricting. If so, try Magnums.
Another factor can be that you're not getting enough mental stimulation. Yup, the brain is still the biggest sex organ for all of us. If it's the same in and out, you're not going to blast off that easily. Try something new - how about ANAL sex? Maybe not as the main course, but as an exciter...and then go into p-v sex for a while (change the condom inbetween) and then finish with a handjob/blowjob while she sits on your face and/or tells sexy stories?
And I'm assuming you know that smoking and drinking affects the penis in a big way. So can heavy meals, stress, both physical and emotional. In addition, if you are on BP or diabetes meds, or even antidepressants, this could affect your entire orgasmic capability. And finally, masturbation can be a big bugaboo. Too much can interfere with the capacity of someone else trying to get you off, since your sexual scripting becomes so habituated to your own hand, so to speak.
One last thing - if you are seeing providers, do you keep switching or is it the same one? Sometimes going to see new ladies all the time can induce nervous excitement. On the other hand, if it's been the same one for years, try someone else. You may need new visual stimulation, as the brain can outwit even the best of penises, LOL.
Hmmm...what else did I forget,
The Love Goddess