If you think you have been working hard, then it should reflect on your grades. You clearly said you have no notes, and barely did past papers so it's pretty obvious why you have bad grades. So what did you exactly do as 'hard work'?
I know I shouldn't be saying all this as I Ieft revision until 4 weeks before, but I was stupid and thought GCSE's were pointless (still managed to get all A's tho hehe)
It is only February, and have you finished all the topics though?
Anyway, what you want to do is experiment with different kinds of revision methods and see which is the best for you.
But I suggest you read through all the textbooks for subjects like sciences, R.E or geography, try to learn a majority of the info day by day. You also don't need to do a lot of hours yet. Then apply what you have learned in past papers. Keep grinding and soon you will learn how the exam board wants you to answer questions.
I only used past papers and nothing else to revise. No notes, nothing. Mainly because I had no time
All I did was try past papers then if I got a question wrong I would check my school book or revision book from the exam board (if you don't have any, you can try your local library as I couldn't be bothered to buy them lol) to help me answer, or if I still don't get it I would copy it down from the mark scheme and learn it.
But obviously, as you are not me this method might now work for you. Many people also find flash cards really useful. (I used flash cards only for Welsh, which was a few months before my main exam period so I experimented a little.)
For maths, you just need to keep doing questions and past papers, that is the best way.
(Sorry if I sound aggressive at the start, I just don't know how else to put it xD )
Good Luck