struggling with a level physics

Recently, I've been having a lot of trouble with A Level Physics. I know its meant to be a difficult subject but everyone else in my class seems to be doing decent and I'm just doing ****. I spend a lot of time trying to revise but none of it actually goes in. Its getting really frustrating and I'm beginning to get stressed about my future and what I'll do if I fail. I love physics, and I came into sixth form hoping that I'd be able to study it at uni because I find it so interesting and I think it's such a cool subject, but now I'm starting to doubt is that'll ever happen because I just can't seem to wrap my head around a lot of the content. I don't want to give up just yet, but I'm worried that I'm running out of time to get my **** together and start getting decent grades. I also find myself being busy a lot of the time, I have a part time jobs and recently I've been on work experience. My sleep schedule has become *****y and most nights I'm only getting about 4 hours of sleep. Does anyone have any advice on improving my grades and managing my time so that I can spend my time revising efficiently? Any help appreciated, thanks.