Carpal tunnel, ulnar nerve entrapment, to name a few.
Several possibilities. I had similar symptoms and they found spinal stenosis along with a pinched nerve. The options available to you today, if that is the diagnosis, is better than it was even 10 years ago but, if you have a neurosurgeon for your existing back problems, I recommend seeing him/her soonest.
Good luck,
BeHill
Are your back problems in your upper spine? If so, it may be a compression of a nerve or blood vessel. I would recommend speaking to your doc to have imaging done.