What Causes Constant Nausea, Severe Stomach Pain And Weight Loss?

over the pass month I ve had my daughter to the hospital 4 times. The first time it was because she had been sick for 3 days. Not able to keep anything down including water. The hospital hooked her up to IV and gave her medication to settle the nausea, took blood work and told us nothing showed it must be viral. 2 days later I took her to another hospital with the same symptoms and no improvement from our first visit. This time the hospital found out she was very low in potassium and gave her potassium through IV as well as a prescription for a couple of potassium pills. This worked for a few weeks (since May 18th 2017). On June 20th I took her back up to the hospital for the same symptoms again, but this time she had cramps in her stomach on the Sunday prior (this is when she started with the vomiting again ). Again she was hooked up to IV and medication to calm her nausea and sent home. Everything came back fine. Took her back to the hospital today with her crying in pain because her stomach was hurting so bad. This time they did blood work (for the 4th time) as well as x-ray. Still everything comes back not showing anything. It s being dismissed as viral. They gave her APO-RANITIDINE 150 MG AND METONIA 5MG. My daughter is 19 years old and I m very concerned for her and getting frustrated that she still has this on going problem. She has eaten some chicken noodle soup and a few crackers. This is the first she s been able to eat since Saturday. She s loosing weight, which she can t afford to loose. Please help me. Point me in some direction to question further.