Don't feel like your life is ruined!
I take it you're about to go into year 13?
You can resit a lot - I resat 5 I think and I only applied to Russell Group unis and the situation was the same for a lot of my friends. Something to think about though is that you are doing that on top of your A2 work, and in my experience it does really take time out but it is possible if you can manage your time well, especially if you start revising now and work out the kinks before school starts. Another important point is that some modules are quite easy to resit if you are taking the subject to A2, for example, maths (if it's the same topic because you are building on it anyway so you should be better on it) for example I retook FP1 but because I was studying for FP2 I didn't really need to revise FP1 at all. Some subjects, e.g. history/geography/english, will be harder.
Is there a reason (e.g. health) why you didn't do as well as expected?