I have a sensitive stomach and feel nauseous easily. sometimes the nausea gets worse, at nights usually. in those times, i usually take pantoprazole 20 mg to ease it. but this happens every now and then, and i don't know why?

I am not sure if pantoprazole truly alleviates your nausea or that is a placebo effect. Because your symptom occurs randomly and usually at night so I wonder if is associated with foods at the dinner time or you are too full. You should make a diary about the symptom, big or light meal, fast or slow eating, etc. then you may come up with an answer.

More information is needed to define the cause of your nausea. If the pantoprazole truly helps, one might believe that the nausea is related to stomach acid, perhaps to acid reflux, but a history and physical and perhaps some tests are necessary to try to defined the situation better.