No you're not making the wrong choice. What makes Medicine such a great career anyway? You work like 70 hours a week, get no time for yourself or family and you get paid not very well at first plus you get sued all the time! If you wanna be a doctor, that's brilliant and it is a good job - but if you don't, then objectively speaking, what makes a doctor any better than a teacher? Without teachers, no one would become doctors in the first place!
If you found Maths at GCSE remotely difficult I'm pretty sure A-Level Maths would be hell for you. Chemistry at GCSE is fairly easy and if you didn't understand it, you're not gonna cope at A-Level. And if you're gonna go onto becoming a doctor you must have AAAA in all your subjects or your chances of getting in are remote. So if you're not good at the subjects anyway, what's the point in taking them? You'll only come out with B's and C's and that's not enough to get you into Medicine in the first place.
Take whatever it is you love. I took Neuroscience under the influence of my parents at uni and sincerely regretted it. I am now transferring to do Art History and restarting my year this Sep and I can't wait. In the end, this is gonna make your career and you're gonna have to live with it and you and you only will have to live with it, not your parents. So do whatever it is you love. And trust me, being stuck simply doing a subject you dislike is hell - I've been there lol. And knowing this subject is getting you to a place you dread to be in is worse. I was in tears when I realised my parents don't disapprove as much as I thought they would - when my dad told me to switch courses, I cried so much cus I was so overjoyed. Lol see the relief? You don't wanna be stuck doing something you don't wanna do. Trust me on this one.