Op,
It's something that you were giving each other orgasms through foreplay. Did he reciprocate on the oral front? If not, it sounds a bit like it was all about him - although I could be jumping to conclusions...
It also sounds like that side of things has also died out.
He may or may not have seen his GP. In my experience, GP's are quite happy to prescribe Viagra. As I said before, it can now be bought over the counter, (although some Chemists like you to have seen your GP beforehand), so he really doesn't have that as an excuse.
His ambivalence towards you is very much him, not you. It's very easy for you to believe that there is something wrong with you - I'm sure that there isn't.
@DevonshireCat brings up valid points. Before you get into discussions, think about what result you want. Expect the best, but maybe be prepared for the worst.
He will have to want to change, and it doesn't sound like he wants to very much right now.
You have been with him all your adult life - it's going to be incredibly hard to visualise life without him, so you might have to decide if you can put up with no sex life, and from the sounds of it very little intimacy (obviously, there are toys and things, to help with self pleasure, but it's not the same), so that you can stay together, or whether it's time to call it quits, and find someone that will give you what you want.
As to how to start the discussion, if hotels where open, I'd say maybe do it away from home. Book a room somewhere, and sit him down.
Be open and honest with him. Tell him what you want from the relationship, and ask him what he wants. Be prepared for tears.
I've been where you are. I know how hard it is, and I really feel for you.
Have a long distance virtual hug!
I'm lucky, in that I still have a good relationship with my XW - I still love her, but in a different way - but I simply could not live the rest of my life with no sex, and very little intimacy. Something had to change.
I did what I suggested to you. I booked a hotel, and we went away for the weekend. I was incredibly nervous, and she knew there was something up.
We got to the hotel, and I sat her down in the bedroom, took her hand, and said something like, "we have to talk". It all came flooding out. I found myself repeating things like "I still love you", and there were tears (from both of us), but no recriminations.
Since then I've found out that she suffers from depression, and that the menopause hit her hard. She lost her libido, and had some major body and self image issues. Of course, me being an idiot man, missed all of this... (It didn't help that I was working away from home a lot)
I don't regret that we divorced (well, I'm nearly sixty, single and haven't had sex for some time, but that's a different story!), but I do wish that we had talked openly and honestly earlier - maybe we could have found a way forward that would have worked for us both.
Sorry for the rambling response...