Check your history. Probably you didn't enter your username, password and 2fa code on Bittrex site but on a site with a very similar address.
How did you get to their site? Searching Google for their name or address? Writing the website address?
Hello poordeveloper
Thanks for the info with the similar address...i will check this when im back home from work.
And i got on their site by typing "bittrex" in the address bar of my browser and then i got to the loggin page...as usual since i got that address im my browser history.