I am recently diagnosed with BFS and have had all the work up for MS. I do not have MS and neither do you. I HAVE THE CALF TIGHTNESS you explain to a tee. It will be when I have done nothing physical. This is text book BFS. You can go to the aboutbfs.com forum and type about this symptom and find you are in great company. This is nothing like spasticity. This is where you are unable to walk, or extreme difficulty. I find that it helps if I stretch my calves on stairs. I think this could help as well. I find that I get this when my anxiety is extra heightened. I have had the twitches, numbness, tightness, pain, burning, pins and needles that stay and stay. It is scary, and I go in and out of concerns, but my symptoms fit BFS so perfect and the neruologist is confident that is what I have as well. I believe that you are dealing with the same thing. Calm the anxiety and the symptoms should calm as well.