Hi Nixa, they make a kits for this,follow instruction exactly and you will have a nice looking tub again
Yes these kits do tubs as well, or you can hire someone to come in and spray it for you
As stated above, they have the kits at home depot with step by step instructions. Prep is very important. Just know It is kind of fragile. It will peel if scratched.
My best guess here is that you are cleaning with the wrong products and incessantly (yet unknowingly) scrubbing the factory finish right off. What is the surface of your tub?