I get this on and off too. I get two forms one is like if you were rubbing your feet on carpet super fast and another is like what you state like bites . I notice the bites when I lay still in bed. I always though feel like things are moving in between my skin and body. That probably makes no sense. Anyhow a few thoughts are you on any new meds? Do yo uhave tightness? I ask cause I think for me some of the sensation is from being so tight as well like a circulation issue. I don't have fibro but have PN and have heard them talk about the pins feeling. The only aids I can think of is baths or epsom salt ones,supplements and meds that help calm down the nerves. Are you on any? I wish I had more answers and help for you cause I was not and I am sorry but can relate