First off, Yes you do have to take relevant AS subjects for example you have to take Biology if you want to go into the field of medicine you can't take Computer studies and expect to be accepted.
Take Psychology, You're the one whose going to have to do it, not your parents. You have to do something you love. If you don't you'll hate yourself for it and you'll hate your job. Psychology also pays good.. BUT Don't take psychology because your advice tends to be good because normally you'll have to give advice thats in a book because you won't have gone through the same thing as the patients have also, psychology is honestly one of the most depressing jobs ever!
You'll have to hear people crying and complaining all the time and in some cases patients will wake you up in the middle of the night because they need to for example in some cases of Germaphobes the patients will do so if they touched a seat on the bus. Yes, it doesn't seem easy, because it's not.
Good luck in choosing. Make a Pros and Cons list before choosing and search online for usual Psychology cases and such If you find that you'll deal okay with it then its your choice if you don't forget about it.