I have a humble theory about all of this. I also experience numbness, tingling, brain fog, and periods of confusion accompanied by an anxious feeling. I, too, had a negative brain MRI.
First of all, I firmly believe this is Sjs related. I don't care what anybody says. After hearing of this symptom over and over on these boards, it's got to be. For example, neither my co-workers, friends nor my husband have this problem!
Second, I believe there is a psychological component at play, too. I have been paying close attention to how I feel. It may start with feeling a bit off. My husband will look concerned and point out something really ditzy that I just said or did. This is usually followed by an exacerbation of my symptoms. In other words, when I sense (or someone points out) that I am having neuro symptoms, my anxiety amplifies everything. Pretty soon I feel like I can't make my limbs work right and like I might faint. My brain really goes on vacation.
What I have tried to do is focus on something else. I replace worrying about myself with positive thoughts, like "I'm okay now." If I'm walking and I feel like my legs are going to give out, I refuse to stop---I push myself to keep walking, saying to myself, "I'm okay." Soon, I start to feel better. Meditation also helps a lot.
I'm not saying this will work for everyone, and neuro symptoms should definitely be investigated. Maybe this will be helpful to just one other person, and that's a good thing!