Take a breath. Break all the work you have to do down. Consider the amount of the time you have left and set up a realistic goal that you will need to achieve and maintain each day. I tend to advise not to be very restrictive and ascribe particular times, but just make sure that if you've got to get some C4 done, for example, you do it on that day.
The worst thing you can do now is open up your textbooks and try to soak up a tonne of information. Our brains are not machines - they have capacities and limits before they start going slightly insane! Just do the best you can do with the time you have now. Forget about what you could have done, because that will just reduce any of the time you have now; focus on what you can do now and do as much as you can (that is, within your functioning limits).
Don't overwhelm yourself. Take it bit by bit. Try to make sure you understand the concepts and avoid pure memorisation. Sometimes it is good to consider the bigger picture when looking at topics, before zooming in on the micro-details. Practice with question papers and just, as I said before, take it as it comes.
Hope it works out for you