I've experienced twitching very similar to what you're experiencing. My index finger jumping, at one point my pinky toe on my right foot moving up and down, thigh muscles, back muscles, around the eye,... if it's a muscle, it twitched at some point. Of course my fear was ALS thanks to Dr. Google. But all the anxiety started because doctors were concerned my wife was showing the early signs of MS. So over the next two months and after a meeting a lot of Dr's a learned a lot about HA's two favorite neurological diseases.
Having twitching all over is not the way MS nor ALS first show up. As the MS specialist explained to us, having symptoms bi-laterally throughout your body points away from MS. The disease attacks the outer covering of the nerves starting in one area of the brain or spine. So in order for you to be experiencing physical symptoms all over would mean that the disease had attacked multiple places along your spine and in your brain. This would not be possible until years into the disease and other symptoms would be much more pronounced.
BFS is diagnosed by eliminating all other causes. You can have a MRI, an EMG, blood panels and such and when it all comes back clear, the diagnosis will be BFS. But without any weakness (true weakness - like falling over or not being able to turn a door knob) or any other major symptoms, I'd focus on the anxiety. I know it's scary and I sat there and worried about these deadly diseases for about three months and just waited for things to finally get worse. Then I attacked it like it was anxiety and things started to improve dramatically. It's hard to accept because the physical symptoms are so annoying and scary and your doing body scans every 5 minutes. But if you can addressing the anxiety it will gradually get better. Hope this helps.