Hey, i'll be honest i can't really offer much advice but i know exactly how you're feeling. I'm doing biology(AQA), chemistry(OCR) and criminology (WJEC) and i'm not stressing at all and can hardly remember any content for biology atm.
For uni i only need BCC and i'm predicted AAB and in my last mocks got AAA and with the way criminology is assessed i've already secured the B i need, which definitely isn't helping with the need of like urgency.
I'm always happy to try and explain stuff that i understand in biology and maybe chemistry even though it's a different exam board. For organic chem, have you got like a reaction map, cuz personally i wrote that out everyday until i remembered it but i love organic chem, and i find it the easier topic area for me rather than inorganic and physical chemistry.
I know this might seem weird but Biology from what i know may be the easiest to get an A in as the grade boundaries are a lot lower (at least for my exam boards) compared to chemistry. Plus i've been told that AQA essentially recycle questions so learning mark schemes may be quite good, i also find that Miss Estruch is quite good for 'predictions' as she does a lot of past paper analysis where she essentially tells the likelihood of something showing up.
Sorry this is quite long but you've totally got this and there's still a month till the 1st biology exam. 😊