How long does GAstritis last?

I am just curious, anyone who has healed from their gastritis, how long did it take for yours to heal? Its been 3 1/2 months so far for me, and still feeling rally bad.

Also, If I went from pantoprazole to Prilosec, would that cause an acid rebound effect? I am taking the same dosage on Prilosec as I was pantoprazole (as per doctor), and I have noticed more acid reflux and the burning stomach and nausea is back. Not sure if this is temporary as my body gets used to the new medicine, of if it is just that the new medicine does not work as well.

Any thoughts are really appreciated!