How to help irritable bowel syndrome?

So I'm thirteen and I have ibs pretty bad it sucks. Like today I was at the beach and I ate lunch with my friend and I had a terrible stomach ache going back and forth to the bathroom. Its pretty embarrassing. And every time I went back to the beach I took three immodiums (anti dihereal) and it barely helped witch was strange. Normally I get these stomach aches when I worry about getting them I think that I'm going to end up getting a stomach ache then I forget about it and think it won't happen and then it does. I just want to no if anyone knows any medicines that help them with this. Or if you have the same problem and how you deal with it. Please no mean answers I'm being serious here and I want to no how to fix this problem it's been bothering me for about four years and I'm tired of it. Thanks for people who actually answer :)