Disappointed AS results What should I do next?

I achieved B+CDC (Chemistry, Biology, Physics, Geography) in my AS this year, and I'm not pleased since I want to apply for medicine. I'm especially annoyed at my biology grade because that's usually my best subject, I got As in two of the units but the third unit I got U, that's why my biology mark dropped down to a C. My school suggested I repeat my whole AS year again and basically not apply this year, however will it hurt my chances at getting into a good university for medicine? I suggested I resit 3 units, unit 2 from biology, unit 2 from physics and unit 2 from geography while taking my A2s (since I could very well get an A in biology and raise my geography mark to a B or an A and my physics to a C at least) but I will also take a gap year after my A2s to gain experience to put on my personal statement, thus I don't have to apply with the bad grades. I'm really confused overall and I'm not sure what I should do?