If you haven't specific insurance for that, discuss it at the Gluten Free Forum, there are lots of members from the U.S. there, some of them will have been without the insurance for it & can almost certainly offer practical guidance. They may not be very familiar with bipolar but hopefully that wouldn't stop it being a useful discussion.

If you carry on with meds perhaps after renegotiating the dosage, and then having a few weeks while you find out things, it will be easier to tell what the effects of a diet change are.

I made a diet change after which my GP of the time commented that I was much calmer. (He didn't run all the tests and I didn't know enough to ask.) Then I changed back but that's a long story

It can look like a conundrum but discussing complementary aspects of health at different forums could help, along with making the best use of professionals. Sorry they've not been too good in the past. I ran through a patch of having lots of those too.