It sounds like it could be a lacto infection- cloudy and sour lead me to think that's what it is.
I'm not sure where you would have picked it up. It's commonly found on grain (that's why we boil the wort after using grain, to kill those critters) and it's found throughout many households. Usually, if it's lacto, it'll get worse. The beer may get more sour with time, and then start to gush out of the bottle when opened because the lacto keeps working. So, if it's lacto, and it tastes pretty good, drink it while it's fresh!