Help please

My son is 16 months and he walks great ,mostly runs but yesterday morning I noticed he couldn't get up and stand or walk without falling straight on his face,he also usually takes atlesst one or two naps a day and yesterday he wouldn't take a nap and he wouldn't take a Bottle at all ,he finally went to bed at 10 pm woke up at six screaming ,so I call the nurse hotline and take him to the childrens hospital ,they say they can't find anything wrong and he is still acting the same except he can stand but he is still wobbly. I know its a bit confusing but im desperate for someone to tell me theyve been through this ......

No eat infection? With the symptoms being unstable, won't sleep, then wakes up screaming, That would be my first concern.