What Causes Painful Abdomen And Vomiting?

Hi I recently have been feeling ill in my stomach yesterday and realized that it was the stomach flu when I got home my abdomen was in severe pain and I feel like I had to vomit but I couldent get it out so I forced myself to vomit, I would feel relief for about an hour then the pain would come back so I vomit again and again 3 hours later once I feel relief I feel so dehydrated and drink grape juice and it just caused even more pain and I vomited the juice so I see that anything I put in my body just wants to come out what do I do