I would strongly suggest that you do not switch to psychology, because if you are currently in year 12, you will find that we are already well into the course. This means you will have to spend endless hours trying to catch up with it in your own time. In addition, why take it when you don't have direct support from teachers?
I also hate Econ but I pulled through & my exams are in 2 months - it depends on how strongly you feel and how well you feel you can do in psycho, I stayed in Econ because supposedly it's one of the easiest subjects to get a good grade, but it's up to you. anyway, i feel you exactly though :)