In need of some medical school advice!

As you can probably guess from my name if you're familiar with hospital theatre job roles, I'm currently an ODP but I have an opportunity to study medicine. My GCSE's aren't fantastic, in fact my whole education on paper is quite embarrassing compared to the competition I face. I have half B's and the other half C's. At A-level I was quite sick so could only take on 2 studies which I achieved an A* in sociology and a C in theatre studies. I gave up my pursuits of medicine needless to say. As an ODP I qualified top of my cohort at 82% and was awarded an outstanding academic achievement prize at graduation. This then encouraged me not to give up and having worked as a doctor's assistant for the past year I realised which job I'd rather be doing! I've contacted universities which have agreed to have me providing I get a distinction in a medical access course and a good UKCAT score. My problem is, I am SO unbelievably nervous about putting myself out there and taking this huge gamble. I have nothing so far to convince myself that I would be capable of completing the medical degree and the last thing I want to do is drain my poor parents of money and energy for me to pursue a career I'd never be smart enough for. Has anyone ever been in a similar situation and taken the chance? Can anyone reassure me that I'm not wasting my time or offer realistic examples of the work load? My mind is a complete mess over this decision. Thank you!