What Causes Nausea And Slight Stomach Ache?

Hi Doctor, I woke up after sleeping a few hours last night to nausea and a slight stomach ache. After taking Pepto, I tried to sleep only to vomit half an hour later. My stomach doesn t feel too terrible, unless I lie on either side, so I have to lie on my back. I didn t have breakfast or lunch the day before, but I had a pretty big dinner. Could my symptoms be due to food poisoning, overeatting, or something else?