Before we dig deeper Bittrex are scam shady exchanges (https://bitcointalk.org/index.php?action=trust;u=96390).

You are the only one who knows why you are being hacked, try to scan your PC from virus, malware, and etc. Also, What kinds of program that you use your API keys? does it open source or some closed-sourced trading bot scam. Try to remember step by step before your coin get lost.

After all, there is likely zero chance you could win back your coins.