What Causes Severe Gastritis Along With Pain And Bloating In Abdomen?

My stomach always get a lot of gas，bloating and pain very often when in bad mood, very sensitive.
How & where to get PREPULSIDE (CISAPRIDE) ? Or other even better way/medicine to reduce the gas-producing?
Is this a prescription/otc drug on-line?
I am 74 (F) and don't have insurance.
Thank you!