Asking where are you at is a common grammar mistake, and the mistake and error is as obvious and evident as is the redundancy and repetition of the second part of this sentence and complete thought.
More simply–and less redundant–the word where means at what location, so Where are you at is the equivalent of At what location are you at? Ats a problem–if you ask me! Never use where and at in the same question; just ask where are you instead.
I could go on, but I’d hate to repeat myself.
Paul’s book–Literally, the Best Language Book Ever