If it tastes and smells like vinegar and nothing at all like beer, then I am afraid yes it's infected
If you followed a good cleaning and sanitising regime then you have been very unlucky and got an bacterial infection in your brew.
It is unfortunate but it happens
It is worth giving all your brewing kit a good clean and sanitise everything that comes into contact with your beer with a strong chlorine based sanitiser before you brew again :thumb:
oh and if you do use bleach, rinse that fermenter a shed load of times afterward.... like at least 3 or 4.... you dont want a trace of it in your next brew :shock: :sick: