I don't know what job I want when im older

I am 22, just finished University and I too have absolutely no idea what I want to do. At 16, it really isn't a big deal as you still have time to think about it.
I think many people are in this position.

I studied English because I was very good at it and because it is a degree which can link to a good few things, and also German because I wanted to carry on with a language.
If you have an interest, perhaps look up info about possible careers relating to it, to see if it is something you want to study? If you enjoy something, it may be worth studying anyway, as options will develop as you study and after too.

Or take a gap year, try out diff things and then see if something else appeals to you.

Forget about the future man. You will fall into place. Do what you enjoy, get a part time job and earn some money to fund a hobby and a social life. Get involved with the right people, don't just sit around wasting your youth. If you're enjoying psychology then stick at it, get good grades. Do you want to go to uni? If not what could you do now? Anything at all? What about the armed forces? Start a business? You're only 16, even if you thought you knew what you wanted to be, you probably would be doing an entirely different thing by the time you retire. You have a lifetime of choices to make, you don't have to make choices yet, just focus on keeping doors open and maximising your potential. Volunteer, get experience, get a hobby, make friends, live your life.