YOU CAN DO THIS!!! make a plan with short term and long term goals (eg. finish revising physics by the end of term as a long term goal, then individula topics by the end of each week as short term goals)
Make sure you also do some practice questions at the end of each topic, to ensure you have learnt the topics. For example, im doing A-Level maths, so every morning before school ill do a practice test (or half depending on if i have enough time) and mark it when i get home. Also use the spec to make sure you havent missed any key points.
Prioritise subjects if you have to, spend more time on the core subjects as they are by far the most important.
AND JUST REMEMBER, take regular breaks and find what motivates you must to work hard and efficiently. Make sure you get enough sleep each night, if you dont it will affect the rest of your day and you wont be as productive as you like.