I Am Having Dull/achy Pain Across My Back, Upper Abdomen

I am having dull/achy pain across my back, upper abdomen area for couple days. feel full, like I don't want to eat , sometimes feel as if I am going to get sick. did have vomiting episode 2 days ago - severe vomiting with white ish fluid that was very acidy/burning when it came up. feel fatigue , had dark colored urine for last couple of days but it seems to be going away/getting lighter