Will the brain/cns go back to normal after stopping xanax (alprazolam)? doctor explained i didn't need taper after small doses over the past week or two.

Yes, eventually: Yes, your brain can go back to "normal" after stopping xanax (alprazolam) -- and it may not be immediate. Also it depends on what your baseline status was. If you were very anxious before xanax (alprazolam), this may recur off of it if no other treatment is being or has been done. Tapering of xanax (alprazolam) and its relatives is needed for best results. I don't know how small your doses have been, but assume your doctor knows.

Xanax (alprazolam): If you used small doses for a couple of weeks, it is very unlikely you have any problem stopping without any tapering.