Oh noooo oh dearie me. Hope you get well soon sweety, thats very unfortunate. Call up your school first thing in the morning or if not, check the AQA website or contact them. If its really that bad, surely you can tell them that you cant make it and get a doctors note to show your circumstances, and then re-take this unit or exam at a later date
I'm not 100% sure, just try to find out. There must be some system in place that allows exceptions for people that get ill