How do I know if I have MS?

You cannot know based on how you feel. There is no single test that makes the diagnosis of multiple sclerosis.  It is a diagnosis that requires several pieces of information.  Even with the appropriate information, sometimes the diagnosis is not certain.

Multiple sclerosis is a condition that causes deficits in the brain, spinal cord or the optic nerves. The deficits are caused by demyelination. This can lead to symptoms of numbness, weakness, visual deficits, problems with thinking, difficulty walking, difficulty controlling bowel and bladder function, or clumsiness. The symptoms depend on the location of lesions that occur in the structures.   Some people with this condition may have a small number or a large number of lesions.

The diagnosis of multiple sclerosis requires a comprehensive interview, face-to-face evaluation, and testing results. Some tests are done to eliminate causes of conditions that are similar to MS. Tests that are commonly used to help diagnose multiple sclerosis include MRI of the brain and the cervical spinal cord (neck) and spinal tap.

People with multiple sclerosis have primary or secondary symptoms. Primary symptoms include a neurological deficit lasting more than 24 hours, such as blindness in one eye, double vision, loss of sensation in the face arm and leg on one side of the body, or weakness of one leg. Secondary symptoms include fatigue, especially in warm weather, short episodes of numbness and tingling, or the sensation of needing to use the bathroom.

Some conditions are similar to MS but they are not the same.  See conditions like MS

This is a description of the types of MS