Please keep in mind that I have not personally examined you nor have I seen your MRI (which is the basis of the post) and cannot make an accurate diagnosis without doing so. White matter changes, depending on exactly where they are and what your clinical history is, can represent a number of things including non-specific changes that are found in normal individuals. Again, it's very important where they are located how big they are and how they appear on the MRI - but in some patients, it really doesn't mean anything at all and are clinically insignificant. It certainly does NOT necessarily mean there is brain deterioration and is NOT caused by stress.
MS of course is a possibility, especially in a young woman with neurological symptoms. But other common diseases include migraines and microvascular (tiny blood vessel) changes related to high blood pressure and diabetes. Less common diseases include sarcoids, lymphoma and Lyme disease. Good luck with your upcoming appointment.