Hi,
I'm doing my AS' now and I did exactly the same as you last year. I got 3 Bs, 8 As and 2 A*s
Don't worry and don't panic. The best thing to do now is make sure you cover everything before your exams. Prioritise the exams depending on the order, so if your physics and chemistry is in the first week, revise those now and then again just before the exams. You'll probably find that you won't need to or be able to do loads of revision, it'll all get tangled in your brain.
If you're anything like me, little and often is the best way forward. Do 1-2 hours a day in 30 minute chunks with a break. Get plenty of sleep and eat well. Stay positive and it will all be okay!
Try to think of revision as a small job rather than letting it become your sole purpose in life! It's not the most important thing you need to do!!!!
I agree with Fanatical Geek that past papers are really helpful. To be honest I'm still struggling but just try to keep positive and level-headed. Remember that if something goes wrong it's not the end of the world!
Best of luck