im going to be brutally honest for your own sake. like you I didnt do that well with my AS the first time, i got DEEE for biology, chemistry and physics. i repeated AS and still didnt get good results. i then went and did a btec. i was busy looking after my disabled mum and austic sister, i really didnt care for my alevels and i also dreamt about doing medicine to make my family proud. i wish i had taken the advice of doing just 3 AS subjects instead of 4. seriously you wont be losing anything by doing 1 less AS subject, medicine is competitive but you'll still get in provided your GCSEs are great