Does anybody know what's wrong with me? I have bad gas and my stomach feels tight.?

It was hurting last night, but I think that was because I had nachos and the cheese was really spicy. All I've eaten today was: A gl of milk and a chocolate fudge poptart, grilled bell pepper with corn on the cob and easy mac and milk, a fruit pop, some handfuls of chex mix, a gl of water, a protein shake, a potato roll with cheese, and a salad with zucchini, cuber, and croutons. I'm thinking it's just gas, but I really don't want it to be a stomach ulcer. So, can someone tell me what's wrong with me?