Re: White blood cells back to normal...
15,000 is above normal, but not scary high. (Kind of like a fever of 100 degrees. You're definitely sick, but it's usually not serious.) A stomach bug or a minor infection could easily cause that.
With a bad stomach bug, it could take a while for you to recover fully. I remember once I had a virus that lasted about 12 hours, but my appetite didn't come back for a week! Keep eating small portions of easy to digest foods. If a week or two passes and you don't seem to be getting any better, go back to the doctor.