This could have happened to anyone, seriously. You never know if something is going to go wrong on the day and it will all get turned upside down. You'll find that in time you'll accept your grades and realise that
a) they are good grades
b) they really don't matter that much
I don't know what you were planning to do, what course or what university but for most courses and universities GCSE's are just one in several deciders, you have impressive and solid results so you won't be disadvantaged by your results at all.
If you got Cs in maths and english I would say re-sit them, but you didn't so thats fine.
You could always try re-marks or re-sitting but I promise you this will pass and its all about the attitude you have now, if you want to get good AS results then put your head down and do it, if you want good work experience then go find some.
You'll find other people that get higher GCSEs get complacent and don't put the work in elsewhere. If you complete your package (i.e. with work experience, AS levels, personal statement etc....) then I don't see any reason why you shouldn't be in the running along with everyone else.