Gastritis Support Group
Gastritis is a medical term for inflammation of the lining of the stomach. It means that white blood cells move into the wall of the stomach as a response to some type of injury. Gastritis has many underlying causes, from infection with the bacterium H. pylori, bile reflux, or excessive consumption of alcohol or certain foods or drugs like aspirin.

I'm a fan of Zantac+PepZin GI combo. For more, check website in my profile.
What are the possible side effects of PPI
And there is some evidence toward them doing another terrible thing, but until there's a definitive clinical study, I won't be fear-mongering.
How long i should take more. As i m not feeling any pain or any thing else regarding stomach
Oddly enough, my gastritis only had very, very minor nausea that was highly transient, so I guess I am lucky. Nevertheless, through my research, I have a few anecdotal stories and possible meds ideas that you could try.
For me personally, taking Nexium 40mg per day has taken away all the nausea, albeit small, that I had. The doctor prescribed 80mg and even though I believe in taking PPI's as there is real evidence to back up taking them and forums seem to be a taboo place for PPI's, 80mg was simply overkill.
A friend of mine with gastritis didn't see any results whatsoever until he upped his prevacid dose from 40mg to 80mg, alternatively.
If you suffer from nausea as a result of bad tastes, I recommend chewing gum or swirling (sipping if you can) ginger tea in your mouth. Also, gargling ice water helps as well. [All of these apply to treating nausea alone in my experience].
Other meds which require a prescription that might be useful include Periactin, zofran, and marinol (not sure if marinol is safe for gastritis but it works wonders for appetite and nausea).