For the past two days, i have had burning stomach pain and loose to watery stools.i get a low grade temperature at night. there is no intestinal cramping. could it be an ulcer, ibs or virus?

Hard to say: It's not really possible to make a diagnosis without an exam, as with most abdominal symptoms, it's best to be seen by a doctor if they last more than a few days. Could be a virus or food poisoning, if so it should resolve quickly.

Infection: Feverishness & loose stools suggest an infectious process. Viral infections are usually self-limiting (few days) while bacterial infections can escalate to severe illness, vomiting, significant feverishness & dehydration; oft requiring doctor assistance. Blood in stool worrisome. Irritable bowel syndrome is functional disorder without known cause, absent fever, & is chronic (months to years).

Probably viral: Probably viral. You can try pepro-bismol. If not better in 3-4 days see your doctor.