L. - you've received a lot of good advice for IBS - but I want to encourage you to seek a diagnosis from a GI specialist. Your post was short w/out a lot of details, so obviously none of us know all details; however, it may not be IBS - it could be Crohn's Disease or Ulcerative Colitis - which both may present as IBS. (as symptoms are close), but the main difference is Crohn's and UC have no dietary issues - it won't matter what you eat or don't eat. They are both controlled by medicine, but do affect way more than just your digestive tract, such as your joints (feeling achy), fatigue, vision problems, etc. A diagnosis is confirmed with a colonoscopy. Many people with the diseases mistakenly just assume it's IBS and they try to self-medicate, which will never correct the problem. The danger in this is with the diseases, your body is actually voiding the bowels without absorbing any nutrients, leading to malnutrition and other very serious health consequences.
Okay, now after all that scary sounding stuff - it's likely a touch of IBS, but I did want to get it out there that it could be more serious and therefore is worth the time to see a specialist for a confirmation.
Good luck! S.