Childs sick

On the 19th my daughter said her throat hurt and began throwing up back to back. I took her into the doctors for a strep test. The test was negative so they said it was a virus and sent us home with some Zofran. She bounced back to her normal self after the first dose. A Week goes by (now the 26st) and she displays the same symptoms. I figured it just didnt make it out of her system yet so i gave her zofran again. She bounced back to her normal self again. As the week went on she randomly tells me her stomach hurts below her belly button and then her teacher calls and tells me she had 3 accidents at school very close together. I took her into the doctors to see if she had a uti. No uti. Shes been EXTREMELY hungry all week. Now today the 4th she is again throwing up and has the same exact symptoms. The doctors keep saying its a virus. How is it a virus when its coming back 1 week apart for 3 weeks? Has anyones littles experienced this? Any suggestions on things i can have them check?