Why did I randomly get horrible stomach pains after a stomach flu?

So I became a vegetarian back in the middle of November 2009. On February 13-14, 2010 I got a stomach flu thing, where I had the worst stomach pains I ever had. It wasn’t like I felt like I was going to throw up, or had to go to the bathroom or anything. Just an uncomfortable feeling but it hurt. It got so bad at times that I couldn’t stand up. They were like episodes where it would hurt for a period of 40 minutes, and at 25 or so minutes, be the worst part where I couldn’t stand up, and then slowly went away and I was fine for 20 - 40 minutes before they came back. On the 14th, about 24 hours after I first got the pains, they were gone.

But then a few days later, came back for a few hours, but were never as bad as the stomach flu thing I had. (Oh, I also went on a week cruise starting the 14th of february) The cruise was also really rocky because the stabalizer was weird, so I thought I was seasick. But the weird thing was, when I got the pains, They were there for hours.

Now it’s today (March 9th) and I still get them, but not as often. I feel some kind of pressure on the back of my throat/in my esophagus at times, but mainly the uncomfortable stomach hurting feeling. I also feel worn out (tired) and feel like I’m pale, even though I’m not. The pains hurt pretty much when I get up, going away for an hour or so 2 or 3 times a day, but last the WHOLE day. I’m getting mad that I have to worry about my stomach all the time, and was wondering if anyone had any similar problems or tips on what I should do.