K.C.
I'm a bit confused as well. I have an almost 20 month old and his diapers tend to be more on the "mushy" side with a solid here and there. He's also underweight(less than 5%, but healthy as can be), and he doesn't like sweets, but loves fresh fruit which can make the mushy diapers. If he drinks juice that can cause some changes in the bowel also. I guess I don't understand why the doctor would want to put him on medication just because his bowel isn't "solid".
Also, if by any chance he's cutting teeth or working on some teeth, that can cause for runny/mushy diapers as well. Every single time my son cuts a tooth we go through a few days of runny diapers.
Hang in there, I think he's just a normal kid.