If you missed half of year 10 but redo year 11 then will you still not have missed the yr 10 stuff? I would only redo the GCSE's I needed to get on the course i wanted to do next and maybe see if I could do them at college. Would you rather stay at school though because it's familiar? Have the problems that meant you felt unable to attend school been dealt with?
The best thing to do is probably to talk to someone at your school and see what is possible and what they recommend. Check out your other options such as college too, Make sure you get the support you need whatever you do,