This thread happens every year. Every single year.
Year 12 students thinking that they have been given unjustified marks but the fact of the matter is you simply haven't worked efficiently / hard enough. If you work properly / well enough you DON'T get bad marks. Get your papers re-marked, but 9 times out of 10 you haven't done as well as you thought you have. You may have the odd exam but to get C's all around is just screaming that you haven't done well enough.
I got CCD or something stupid at my AS, and now I'm finishing A2 with A*ABB. Trust me, you haven't come to the realisation that AS's are hard. Watch out for A2 too, there is also a jump in that.
You are all probably still in denial, but the first step you have to make to improving your results is to realise that the techniques / timetables you are using to revise are simply not effective. Wake up and realise that you are wrong. Next year you'll only have one shot at it too.