You may have fibromyalgia. I'm not a doctor, but it sounds like the beginnings of my fibromyalgia.
Although the neurologist did not pick up any nerve damage causing your symptoms (which is a good thing), does not mean that there is no problem.
If you use your hands a lot, the muscles, tendons and nerves can get overused and cause problems.
Having spinal problems, in the neck area can cause referred pain, pins and needles in your arm, hand, fingers.
Pinky and ring finger pins and needles can be due to pinched nerves in the cervical area (your neck).
Using your hand/s a lot, if your job is very repetitive for example, can also cause tendon and ligament problems that can cause you to feel the symptoms that you have.
Have you been to see your doctor or a physiotherapist? A physiotherapist or chiropractor can relieve any spasms in your neck area or misalignment of any of the vertebrae that may be the cause of your problem.
If you do have a very repetitive job, you may need to consider resting and supporting the "problem" hand to allow it to heal. The clenching thing may be due to tendon issues rather than nerve issues. I do not know which specialist would be responsible for any tendon issue problems, your own doctor may be able to give you advice with regard to that. It may just be a question of using a support splint to allow any tendon damage to heal (which does take time).
Best wishes.
Well Jen, now that several other issues have been ruled out, perhaps it's time to get some allergy testing done? Allergies can affect people in multiple ways, and perhaps yours is by these tremors, tingling, etc. Does anyone in your family have tremors? Familial tremors is utterly possible, and it's utterly benign except to those suffering from them (embarrassment, anger, questioning, etc). Were you prescribed some vitamin B6 for your deficiency? Maybe if that can get back to a normal range, you'll feel better. Given that many things can create this deficiency, you're going to have to look at what may be causing it. Alcoholism, genetics, birth control pills, other drug reactions/interactions, starvation dieting, or persistent chronic diarrhea. Just so that you are aware as well, it can lead to and has been associated with many different psych disorders. I hope you can find the cause and I wish you much luck in doing so!