It's been over 2 wks since my 13 month-old drank anything and now is refusing food, what's wrong with him?

The problem with children not drinking is that they can get dehydrated very quickly. I would take him back in for another strep test and make sure they do it really good. Some doctors will say that children this young typically won't get strep, but it is possible (from experience). This does not sound normal to me. Keep taking him to the Dr. or if nothing is done there, take him to the ER. If anything, they can give him some fluids IV and that may perk him up. One thing that I have learned over the last 8 years of parenting is that if you just have a gut instinct that something isn't right, keep pursuing it. Good Luck.