SERIOUS SCHOOL ISSUES!!!!?

I am considered a bit of a geek in school - getting lots of awards and stuff - but I'm really not that bad...:) Ever since the Christmas holidays ended though,my standards have been slipping and right now, at the end of year 8 before GCSEs, that is not good!!!!I have a rocks project and end of year exam for science, HUGE project for art, transitional high school tests for english, math and french and to top it all off other homeworks aswell! I'm really stressed out and want to do well in high school but then again I just want to relax and cool off. Any tips on how to organise myself - you would not believe the amount of timetables and diaries I have so just and other ways of structure PLEASE!!!!