What do you do when you can’t control your child’s fever with medicine?

It Depends. Fever is an immune response to fight the infection. What do you mean by "control"? Making it disappear when a child is ill with medicine does not usually happen. Most pediatricians worry if the temperature is over 105 or 40 degrees centigrade. More important are the other symptoms -- pain, lethargy dehydration etc. With these parameters go to the ER or call your pediatrician.