Just keep at it. The thing with the current system is that you can play it so you can easily get a good grade by retaking lots of times. This is frowned apon by most, but its your exams and your life.
I did Alevel Maths, physics, economics and geography + AS computing. Im far from the conventional idea of clever(got Cs and GCSE) but still managed to get a AABCb at Alevel.
Just try to find a studying style that suits you. Im doing an engineering degree, for me its lots of repetition and copying out of books, memorising techniques and also doing a few questions. I usually use up a few A4 pads (1000+ sheets for a few exams - front and back) when revising. People think ive done LOADS of work but really ive just been copying and creating links.
If it makes you feel better, I never bothered to work for the jan exams. I just took them as practise, and I usually got rubbish grades. But in June I suddenly got lots of motivation and started to work.