Break it down by day.
Give yourself a treat each day if you finish each bit.
Give yourself a bonus if you get ahead of yourself.
Focus on the technical stuff first (once it's in your head it's easier to remember the "rules" - i.e. Physics first)
Use sites like www.quora.com and www.blikbook.com to help with complex questions
Share timetable with a close friend and get them to monitor you (and vice versa)
You cant get round doing, you just have to get on. There is a program called Phase 6 which is really good for learning facts, you input them and it tests you at various intervals to get it into your long term memory. This might be good for History Make a serious plan, on each day make sure you have at least one subject you find difficult and at least one subject you find easy, start with the one you find easy to get you motivated to continue doing the hard subject