I understand your predicament, since I'm in a somewhat similar position (except that I've already applied for medicine this year). Take a step back and try to look at things from a more objective viewpoint - having wanted to be a doctor for ages is probably clouding your judgment, if you feel you can't go back on a decision you've held for such a long time. It is a huge decision to make as a teen so think over it and don't rush to reach a conclusion... it's easy to overanalyse what each path would lead to after university, but I think there's too much uncertainty to make up your mind based on this. Ultimately I think it's down to you envisaging which of the two disciplines would leave you unsatisfied; I doubt you would gain the same - or even comparable - satisfaction from both, if you analyse your ideals carefully. I'd say you should do maths.