I'd be getting a second opinion too, and further testing.

The only other thing I can think of which hasn't already been said is candida - a friend had it quite badly, and no amount of short term solutions would help, so she's had to go through a complete diet transformation over the past 18 month, to completely clear out of her body anything and everything which can potentially feed the yeast. It was a long and hard slog, but she is so much better now.

Worth looking into.