Although stress can often be physically manifested as neuro-like symptoms, I always try to rule out any medical causes first rather than miss something that is potentially treatable. I haven't heard of stress causing a B12 deficiency, but B12 deficiency can cause several different psychiatric conditions such as anxiety, mania, or depression. Also, there is a genetic factor associated with B12 deficiency, so if you have a strong family history it may be worth it to see a physician and have your level checked. The other thing is that your current oral dose of B12 may not be enough if you really do have B12 deficiency. You may need an injection or a much higher dose. All in all, a good physical examination by an internist may point you in the right direction.
Good luck.