There's a very good tooth paste and mouth wash called closys, probably can find at a CVS or Walgreens ( any drug store ). It works really good and is know to work with your situation. Most likely, in your case, you have bad breathe fairly often. When your tongue turns a yellow/ whitish color it is a sign of dry mouth which can be caused by many medications or it's just common for some people. Overall, I hope this helps! Good luck!
It is normal but for good hygiene brush the back of your tongue daily. It is just normal bacteria. Get a good tongue scraper or use the back of a tooth brush that has one. I do it in the morning and at night. A mouth wash can help with flouride or regular type.
mkh9