hey,
ease your mind. you probably did NOT fail. everyone comes out that exam feeling like they failed because you catch your mistakes after you get out. However, I think if you were nice, remembered to watch your hands and did somewhat decent... you probably passed.
As far as how soon you can take it, I'm not sure about that. Check the USMLE website. But seriously, don't worry about that until you get your results and you will be surprisingly pleased. 🙂