Year 12: Medicine application

I am a year 12 student studying biology, chemistry and psychology.
I really want to be a doctor but I haven’t really began anything to put me in a position with a really strong application for year 13.
The problem is I don’t really know where to start, I’m not sure how to get work experience and idk how much I should try and get and in what areas. I also am not too sure how I can get volunteering placements.
I’m also aware I may need some sort of awards, so what can I try do that would work.
Please can someone give some advice I’m very stressed about this