Macbook keyboard issues?

this problem just started recently, and i don’t recall changing any settings that would account for it… whenever an action key (like shift, command, etc.) is pushed and released, the next key hit will be affected. like, i don’t have to hold down the shift key to get a capital letter, just push (and let go of) shift, then push a letter, voila, capital. doing the same thing with command, function, option… all those. it’s getting very frustrating as it’s making me do things i don’t want, like quitting apps and whatnot. anyone have similar problems? know how to change it back?