I don't think they'd make you redo the whole year, you'd probably just get the option to retake a module or two. Don't panic, that'll make it worse and you'll get a complete mental block in the exam. Just tell yourself repeatedly 'I know it' and you'll be in a better mindset. Don't worry, I'm in the exact same boat as you, currently trying to cram for my exam in the morning because I didn't revise until today. Just try to make use of the time you have left as best as you can