So you are 17/18 and studying at high school level in the UK, with another year to go?
If you check out the UCAS handbook (your college should have a copy of this year's) and/or university websites you will see the expected grades for entrance to a UK medical degree straight after high school. Unless you have some other outstandingly remarkable qualities and experiences, BCC at A level won't do it.
If you are looking at US medical schools, they are almost all postgrad schools, and you would need to get your undergraduate degree first. Even then, very few take international (non US citizen) students.
You are young enough to have a lot of options still open to you. Firstly, talk to your college (find a friendly teacher/lecturer or academic adviser) about how you are doing, with an analysis of your current study habits. Work out what needs to change - work on removing any bad habits you have got into, and find the best study style for you personally. You may find that your grades improve.
Secondly, are you doing any volunteering which gives you exposure to patients in a clinical setting? Until you have spent a good deal of time around sick people in a professional setting, you don't really know what a medical career means and whether it would suit you.
Thirdly, there are a lot of careers which relate to medicine other than being a doctor. Apart from all the very many highly regarded associated health professions, what about medical research? health policy? Admin/management? Charity sector?