I'm going against my parents wishes to go to study medicine
Why would you turn down a chance to go into medicine and not go through with your parent's wishes?
Because it's my decision, why should I do something because my parents wants me to?
Your parent's wishes might be too strong for you to handle, and it is your life in the end. Your parents just want the best for you, try to make an effort to go at least one year to study. Otherwise you won't even know if you like it or not, and you could still change your mind either way.
I cannot stand their strict rules and it's time to stand up against them.
While I agree that you should stand up for yourself, I feel like ignoring your parents wishes may not be a good choice specially if they are the ones paying for your college. If you can't convince them respectfully that medicine is your preferred study, then I think that it's time for you to find another place on your own and be independent so that you won't depend on your parents.