You poor thing, sounds really horrible. I haven't trawled this whole thread, so forgive me if my comments are superfluous but is the bike you generally ride specially made for you? If like me you are not a standard size, then off the peg bikes rarely, if ever, fit well enough to ensure cycling more than a few miles doesn't result in pain in one or more body areas. I have never had the nasty problem you are experiencing but my daughter suffered extremely sore buttocks which disappeared once she started riding with drops, and using a Brooks. This was most likely due to the fact that lthe new bike fitted her much better and less weight was bearing down on her sit bones, rather than the Brooks (although I do love those saddles). Your problem sounds much more severe than hers ever was, though, and I think if it were me I would adopt a two pronged approach
a. Get the opinion of a sports injury specialist (if you are in London and your own NHS practice won't stump up, the Crystal Palace sports injury clinic is very reasonable)and very good, at least it was for me) and
b. Contact a bespoke frame builder who will measure you up really accurately. When I had my Roberts made I was amazed at the attention to detail in the measuring. I had expected a jig but instead found they personally measured what felt like every bone and joint to joint distance I had. Admittedly, expensive but, for me, it has been easily worth every penny.
Best of luck
Jane