My right hand is not able to write for an year now and it used used to write perfectly...it experience tremors and stiffness when i'm trying to write..?

You should have this checked by a neurologist to find out what is wrong with your hand. You need to find out if it is an issue with your hand alone or if you have a systemic issue. A neurologist will be able to examine you and get the necessary tests to diagnose the problem and hopefully treat it. Good luck!

Sounds like a movement disorder, a dystonia, commonly called "writer's cramp". This is a localized problem and typically not a sign of future more widespread issues. It often responds to Biofeedback Therapy, but medication may help. See a neurologist or a hand specialist and get this addressed.