I'm scared i have ms...or some nerve or muscle thing...i dont want to die...please helpp?

ok im 16 and for the past few months my arms and legs and just my body in genral have been kinda twitching its not noticable to anyone else but me is kinda like it jumps for a half a second..when i think about it ..it seems to happen alot more..then when im doing something and not thinking about it i hardly notice it all..i went to a neroligist(sp?) and he did like a basic exam and tested my reflexs and other stuff and he said everything was normal...this has been happing for the past 5 months..it comes and goes..im scared i have like als...or ms or something...what could this be if the dr said i was find...also sometimes when im writing or playing a video game my fingers kinda become stiff...im really worried and im freaking myself out

If you have gone to a neurologist and been given the OK,it is likely that you are ok.However,if you do not feel confident in the answer you have recieved,you should go to another neurologist for a second opinion.
Also,if this occurs more when you are thinking about it,it is unlikely that it is a serious disease.Your fixation on it,in essence,makes it happen more or appears to happen more.
As for your fingers becoming stiff when writing,this sounds like carpal tunnel syndrome.It is caused by repetitive motions such as typing,writing,or using a video game controller.The blood vessels in the wrist become constricted,leading to tingling,numbness,or stiffness.I would suggest going to the doctor for this as well.It is not life threatening,but if left untreated could lead to surgery.
Be safe,don't worry yourself to death.You will be fine.