Can too much water cause a fever for an 11month old?

So im at the er and my baby had a constant fever that wouldn't go away. Since he ia 11months going on a year..

I just started feeding him solids and saw he was getting constipated so i gave him more water like id fill his zippy cup up ..

The Dr said his fluids are low and hes dehydrated bc i gave more water..

I fill so stupid. I thought water would keep him hydrated. But hes drowsy and abt to be admitted.

Pls no mean comments. He is my 1st and I feel so bad already. Id punch myself if i could.