I wish I could help you, it sound like a nightmare. Perhaps you could go and see a Naturopath? One that specialises in Women's fertility and such. Get a second opinion from a different GP perhaps? Doctors don't know everything, it's a lot of trial and error sometimes, maybe someone different may try a different approach, or may have had a patient with your problem before.
As for the IUD, I was reading up on it the last few weeks, as I was thinking about having one, but I read too many horror stories about them, I don't think I read even one good thing about them. And everyone seems to have bled for weeks after having them put in.
Good Luck, I hope you can find a solution.