They said i have fluid in my brain stem that's why i see double vision and speech problem but did i get fluid in my brain stem?

Many reasons: Fluid in the brain can be normal or abnormal. There is spinal fluid all the time around the brainstem, but accumulation of fluid such as hydrocephalus and pseudotumor cerebri can cause problems. There are of course infection, tumors and other conditions that lead to fluid in the brain. You need to be under the care of a neurologist and get all your questions answered.