I Was Tested For All Auto-immune Diseases. I Have One

I was tested for all auto-immune diseases. I have one or two symptoms of a few but not at all clearly diagnosed with any. I managed a lot of my symptoms with extreme diet change but I still get extremely over-heated if I work out outside in the sun or in weather over 75 degrees (I live in Southern California). How might I treat my symptoms while still maintaining an active healthy lifestyle?