I have cold and hot chills, feeling nauseous, stomach cramps. What could be the cause?

Ignore no symptoms. Abdominal discomfort of any kind is not to be ignored--its a warning sign that something may be wrong inside your abdomen. Please see my many healthtap answers on the subject of what causes abdominal pain. Not all such problems are serious, but you don't want to miss the problem that is. Your constellation of symptoms may or may not be related. Get checked please.