@SZM: I'll PM you EDIT: Here is My answer to your Query =]
Since you have finished 75 % of the Syllabus I suggest you focus on the 35 % left and just go quickly on the 75 % that is already done at school. In case your school didn't go through it in details then when studying them (i.e. now) pay attention to the little details since they're very important.
I suggest you post your doubts here on studentforums.biz , Hopefully at least half of your Questions would be answered by the time you meat your Teachers. So it wouldn't take you TWO months to just ask your teachers. If studentforums.biz doesn't answer your Questions , there is Xtremepapers.net and many other forums that could answer your doubts including yahoo answer.
If you just study the Syllabus now and then solve Past papers later (based on your personality) , you won't actually enjoy studying in other words you might study just for the sake of studying which results in you not perfectly understanding the Concepts.
If you don't want to take So much time on ONE subject , then throughout the day study THREE chapters/mini-chapter from each subject (bio,phy and chem) and solve the Questions about that Topic until you feel satisfied and put up your Questions. So throughout the day you have Specific Hours to study the Theory part , to solve Questions to make sure you understood it , and to look at your doubts that have been answered on whichever forum that you posted your doubts in. (Do this AFTER you're done studying and solving the Questions concerning your chapter/topic)
Once again do NOT Panic , it will ONLY result in demotivating you which isn't a good thing after all
Ask for Allah's help every time you pray and never give up hope <3
I hope I helped =]
Notice: EVERY single person here will give you a different Opinion/Advice since we're different individuals so it's Up to you to make the decision since you know yourself/what you're capable of more than anyone here does
If you're REALLY confused with ALL the answers you're getting , make Dua Istikhara (Google it to know more). Good luck