How do u know if you have irritable bowel syndrome?

Maybe not IBS: Ibs is a diagnosis of exclusion. The key to your answer: what are your symptoms, duration of distress, & recent evaluation? Do you awakening from sleep due to pain, are your symptoms not intermittent but ever present or actually worsening, have bleeding/fever--if so then it is unlikely you just have ibs. In such a case, further evaluation is warranted to identify the correct diagnosis & treatment.

UBS: Irritable bowel syndrome is a common disorder that presents with abdominal pain, bloating gas, alternation of bowel consistency (diarrhea and constipation). Doesn't cause permanent damage. However, need to have full work up to exclude all other causes. We do have criteria to diagnose ibs. Work with you GI doctor.