The big worry right now is what subjects to take for the next 2 years for the HSC - It really hard to choose when you are not sure what you want to do. I would now suggest that you keep some history or art subjects that you really like and not all the sciences (physics , chemistry and biology) - as it turns out you are not really going to be a pharmacist!
Yes your parents can be a bit frustrating as they are always trying to stop you doing things that they believe may end up hurting you - turns out they are not trying to spoil all the fun !! - they are really just a little too loving and caring - not really a problem in the long run.
Your friends, true friends will be there for you always - sometimes you won't see them for a long time as they get caught up in their own families and lives - but when you next see them the conversation starts as though you were talking yesterday. Many of these friends you will make after you leave school and you are lucky as there are quite a few of them.
Don't listen to the people who put you down or think that you have achieved enough for a girl or for your age! If you are up for the job and good at what you do then go for it - It is up to you how far you want to go. Just remember it is important to want to get up and go to work because you enjoy it - if you don't feel like that get out and change it.
Importantly it is OK Not to have all or any of the answers at this stage - half the fun is finding out what really suits you and what you want to do. Sometimes that can take a little while because you will change your mind a couple of times.
Have fun it is all ahead of you.