I've worked up to 1 TB DE also. I mix it in about 4 oz. of grape juice and drink it quick! I just started on May 3 so I can't really tell if there is any effects yet. I can't seem to find anything to tell me how long it takes to do its thing.
To find an auto immune disorder they need to have an idea of what to look for. Each one has its own markers in the blood and they need to know what test to run to find it. You might consider seeing an endocrinologist or a rheumatologist who will have better training and more experience with auto immune issues.
It could also be a simple intolerance or allergy to something in your food or environment. Have you ever had a blood test for allergy/sensitivities? or a skin scratch test?
Have you're female issues resolved since having the IUD removed?