i know its, sad, but if medicine is what you want to do then say good bye to your social life, come home from college and study study study. write your note up from your subjects, read the textbook and then rephrase it and write it down. do alot of past papers and in chemistry do LOADS of past papers. im on OCR so there arnt many but alot of the legacy papers are virtually the same. practice each calculation hundreds of times to prepair you enough
whilst i agree with salty_candy that medicine is pretty hardcore and not everyone can handle it. but there are many routes into it and you WILLNOT get there unless you study hard. dont lose hope but keep it realistic. remember for medicine you will also need to fit alot of work experience into your holidays ect to boost your application over and above alot of other applicants.