Hi Cooper
My heart goes out to you.... I understand how Dr's can make you feel like a hypochondriac. They are not going through all the pain.
From what I have learnt over the years Dr's can miss the endo when they test for it, if it is not visible they take a scrape of the cells off various organs to see if there is endo cells under a microscope. But they can miss the endo patches altogether.
Go and see the new Dr and see if she can help you.
I was put through the same treatment as you and I still had a heavy period so the gyn up the hormone level with another pill and it didn't work. I could go on and on about what Drs have done and said.
Always check with the chemist about what the side affects are to any medications, because they could happen to you.
lucky you have a great GP

Take care
Chris