thanks guys....
i think my doctor should be okay with it... he knows i have had fainting episodes from being seated for too long as i have low blood pressure, so think i will be okay.... i am going to be honest and say to him 'look there is nothing to stop me from just resigning, i am on a contract and dont intend to go back, but would just feel a lot better having something in writing from a doctor to back up my case'... its basically the truth, i would feel a bit guilty just resigning, plus this way, if i have a certificate i wont feel obliged to give a notice period.
thanks again
(i will be so tense at the appointment i am likely to burst into tears anyway with the stress of it all, haha)