Is it possible to take 2 years out between AS and A2 for ill health?

Hello,
I completed my AS levels at college in July 2013 and then took a gap year between 2013-2014 due to ill health. I started back at college to complete A2 level September 2014 but found i was still very unwell, i am having ongoing stomach problems and have also recently been diagnosed with an underactive thyroid which is causing problems. the college have enrolled me as an external candidate anyway because they were aware of my health issues and knew my attendance would be poor and they said that i could just attend lessons when i was well enough. however i have only managed to go into college twice since september, it is now november and i am finding it extremely difficult to stay on top of the work, especially as i have chosen quite hard subjects, biology chemistry and psychology. the doctors are getting closer to working out what is wrong with my stomach (pretty sure now that it's crohns, waiting for a scan to confirm) and so i should hopefully be feeling well enough to go back to college september 2015, however i dont think im being realistic if i think i can completely home teach myself these subjects while being stressed due to ill health for this year. therefore i am wondering if anyone has taken two years out or knows if it is possible to take 2 years out between AS and A2 or is there a specific time frame between AS and A2 when the a levels need to be completed? i dont want to have to do my as levels all over again if they are no longer valid.i know the college is sticking to the same exam board again so that wont be a problem. any advice on this would be great. Thank you