Regular Diarrhea is a sign of a problem separate from SPD. At least for me, when my Food Allergies cause Diarrhea my SPD becomes much more unbearable. My skin especially becomes untouchable (even touches I would normally like hurt real bad).

Getting my Diarrhea under control was vital to getting my SPD under control. Diarrhea drains several critical electrolytes from your body in large amounts. The more often it happens the more damage that is done to your body and the longer it takes to recover from it. One of the reasons I think my SPD is so bad is I had undiagnosed food allergies for the first 26 years of my life and daily Diarrhea. I had no idea that shit was supposed to be solid until I was an adult and saw an episode of South Park (sadly seriously).

There are several different conditions that can cause Diarrhea and you will probably need to do some investigation work with a Gastroentrologist, Food Allergist, and Nephrologist.

The following problems you mentioned are probably linked to the Diarrhea and if you fix that problem you will fix them.
- Tired all the time.
- Always thirsty
- Lack of sweating which leads to overheating.