H.M.
I have a 3 yr old and 2 yr old. My daughter went thru something similar when she was 1, and oddly enough, we never found out why she had been running a fever. I deffinatley recommend to take her back to the dr. because you never know. However, I often thought that possibly it was her teething. Teething can cause many types of discomforts in children. From fever to diahrrea, or nausea. Don't know if that helps, but I wish you luck in finding the problem. :)