I'm 16 and have constant nausea ...

I am 16 years old and soon began to feel constant nausea. I went to the doctor and he indicated omeprazole, since then I take it every day in the morning. I do the treatment for 1 month, but I do not see the results. I've never had trouble like this before, and it started from day to day, just the day I was about to travel. Nowadays, I get extremely nauseous when I take a test in high school, present a job in public and even when I go out with friends for the restaurant. I'm afraid to vomit. To this day, with these nausea I did not vomit, I tried to make vomit for it to resolve, but it seemed that nothing had in my stomach. He's making noises like he's hungry. I went to the doctor and he suspected gastritis. I would like to know how I can mitigate this problem.