I just want to get something off my chest 😢

I am currently in Year 12 starting Year 13 in September. I currently do A level Maths, Bio and Chem and EPQ. I feel like such a failure because ever since Year 9 I seemed to have forgetten how I should study or revise. Like in terms of whats best for me. I have asked other people how they revise and what techniques (mainly the really smart people) and they tell they just do what 'normal studying/revision is' (I have a feeling that they may be lying and not telling me the truth because in reality nobody would want to share their secret to sucessful grades) I have absolutely struggled. I don't even know half the time what I am doing. I cry and get depressed as I know I am not doing anything properly and am like nothing compared to the people who get As/A*s. Everytime I revise or study there is always this wave of self doubt & not feeling good enough or worthy. Like literally I got so lucky with my End of year 12 Assessments and even GCSEs (mainly because I had to somewhat cheat and teacher's assesing me) - I ended up just passing. I have already wasted 2 weeks of my summer holiday feeling sorry for myself. Havent done any form of 'proper revision' for my subjects and don't even know how? I haven't even finished my EPQ (my essay writing skills are equivalent to a year 7 waffling for english) ! I am doing it over the summer and am struggling to write since I get depressed thinking I cant do it and just start copying and pasting things from website. I don't even know if I am gonna go University of even capable with whom I am and what I am like.