If you haven't entered your details in one of the fake bittrex site than this issue sound quite serious one. I have also enabled 2fa few months ago on bittrex and trusting them with most of my cryptos so I am quite worried right now after reading your case. Do they really have fault in their 2fa? I don't think 2fa can fail at any point because they are tied with google authentication which is based on time and secret code provided by the site. 
Hello amacar2
To be honest, i still don't know if i entered my details in one of the fake bittrex sites or if they did it in some other way.
In a strage way, i'm hopping that it was the thing with the fake bittrex address...so i could say: "S##t...my bad." And this would then also mean, that everything is ok with the 2FA.
Cus, just try to imagine what would happend if the really hacked the 2FA system
