first of all, youre in year 9! ages yet before you have to think about a levels. focus on doing well at gcse first and getting the best grades you can to keep all of your options open.
i would say you should pick subjects you'll enjoy. its a bit pointless to force yourself to study for exams in subjects you hate doing, and even more pointless to pursue a career where you'll find no job satisfaction. think about what youre going to enjoy the most long term.
if youre not sure about career options, maybe try the website unifrog? theres options to take careers quizzes to see what youre best suited for, and really detailed job profiles listing the job descriptions, neccessary qualifications and average salary for each, as well as videos from people in that field. definitely worth checking out, theres so many useful features.
good luck, and don't stress! youre doing great.