What Causes Cramps In Legs And Hands Which Are Like Fits?

i am an engineering student.my age is 22 yrs.i am having problems with my health. Like frequently i gets cramps in my hands not only hands but also in legs.Actually my whole body get twisting structure for few seconds just like fits,but it lasts for only few seconds and then automatically my body recoveres.I have consulted many physicians. They prescribed me calcium tab and some vitamins but it didnt stopped.Also when my mind becomes totally nervous whenever giving any presentation because of fear of these cramps.At the age of 1 yr i got fits twice but after that everything was alright.but i am having these problem since 5 yrs.what kind o disorder is this? is it dystonia?plz give me some sugessions