Used rv possibly making us sick

I would move out of that RV. Could be a lot of mold as has been suggested. Could be a rig that was flooded at one time and they covered up the mold with paneling or carpet, etc. Also, like has been said, do not drink the water. You can sanitize the tank using bleach. Lots of info on the internet on how to do that. I just did mine this week. I sanitize it periodically. I use a product sold for RV water sanitizing, but bleach works too if you follow the instructions. Black mold is deadly. With all your symptoms having started when you moved into the unit, you must get out of there now. It's not safe to live there.

Dale