What Causes Weakness In Right Hand?

Hi, im 11 year old female, for the past 3 weeks or so i feel no power in my right hand and it is also week, it takes great amount of effort for me to write one simple word, 3 weeks ago i could write perfectly and neatly, however there is no problem with my left hand. I dont feel any pain and my right hand is flapping everywhere involuntarily, and is also difficult for me to take control. I have been to the hospital, they told me this was something to do with streptococcal infection in blood which causes neurological problems. I only taking penicillin as an antibiotic as a treatment. I would kindly like to know if there is any other treatment you could refer to me.