I'm getting really stressed about exams, what to do?

I'm so stressed. there just too little time and too much to revise. First 2 exams in 4 weeks but its still too close, there's no way I'm not going to no everything for all in time. I need straight A's, pls no things calling me a geek, these exams are important I never used to take this stuff seriously but really need a future. Just some useful advice. I don t no anything!!! A levels...what did you guys do for them?