Prescription drugs work differently with me?

so i'm becoming a little confused. it seems that prescription drugs have a half different reaction then what they should. the prescription drugs work the way they are suppose too. however like pain killers they are suppose to make you sleepy and lethargic for me they make me energized the same with muscle relaxer and (sleeping pills- so i guess those are the only ones that don't actually work the way they are suppose to) im not sure if this is normal or something is wrong