Testing
Here are several tests you can request from your doctor if you want to investigate the root cause behind your symptoms.
There are many labs that offer this type of testing such as Great Plains Laboratory, Everlywell, Viome, and Genova.
Great Plains
https://www.greatplainslaboratory.com/
Everlywell
http://www.everlywell.com
Viome
https://www.viome.com
Genova
https://www.gdx.net