I have ibs and a history of stomach problems such as ulcers, i recently took 500mg of acetaminophen without knowing each pill was 250mg and am in pain?

Ulcers.: You can take Acetaminophen for pain and fever.You should not take advil, (ibuprofen) Aspirin and ibuporfen when you have ulcer problem.

Usually no problem: Acetaminophen is not particularly irritating to the stomach. I would be careful with antinflammatories such as Naproxen or Ibuprofen (it may be that with your history you don't want to take inflammatories at all consult with your physician).