I hope this helps, I've always had weak muscles that cramp and jerk. Muscle cramping and muscle movements of their own are usually cause by 1 or 2 things sometimes both. Dehydration or low potassium, every night before you lay in bed stand on your tip toes and slowly rock back on heels do that 10 to 15 times. Muscles cramp when relaxed due to them trying to find hydration. I've always found that excessive yawning means my sinuses are trying to clean themselves out. The twitching in your calves can either be dehydration or an anxiety tick. Try to drink 4 to 6 oz water and see if it helps, if not then you need to lay down and practice deep breathing meditation to calm your nerves. Upper back ache could be and is most likely due to stress over worrying. Sometimes I'll sit in my recliner and I'll be stressed and my upper back starts to ache so back I feel like I've twisted myself like a pretzel. I get the internal tremors and I'll repeatedly ask my husband if my shaking is bad and he looks at me like I'm silly. That most of the time is stress or anxiety for me. Again deep breathing helps, but I will sometimes take half my xanax if I cant stop worrying about the internal shakes. Oh and i shake when I yawn too, it's like my body wants to stretch and that yawn triggers it. I hope this helped alleviate some of your fears.