What Causes Weakness In Both Hands And Legs?

My disease is weakness of both hand and both legs.I feel very weakness in my both knee. I cannot standing freely from sitting position.My both hand and both leg strength is very low. I feel very fain in my both leg muscle of under knee at walking period.My both hand vibrating .This problem created sudden after two month ago. Previously this disease was not in my family.Our doctor identify this is myopathy,periodical paralysis.I take many kinds of made-cine, now i feel some improvement.but not completely OK.