What causes traveling tingling and numbness?

I've had a problem with numbness and tingling that is traveling thru my body. Started in my upper thighs where I would have moments of numbness followed by sharp or dull tingling. It then progressed to a place on my left abdomen. Then it traveled up to my left shoulder and it is now moving toward my left breast. I felt the tingling actually on my left breast this weekend. I feel this sensation a couple of times a day. Years ago when it was on my abdomen, my doc did an MRI and said that there was no mass or cancer but that I did have diverticulitis, so I figured that was causing the tingling and numbness. However, that doesn't seem the likely cause now that it's up around my shoulder and chest. Any ideas?