Stopgap measure:
Go and jog a few km. Doesn't have to be long.... just 2-3 km will
do.
Aerobic exercise stimulates the release of endorphins.... they make
you high. Legally. 
It doesn't cost a cent and as a bonus, it keeps you trim and
fit.
Long-term:
Try talking about it to someone. Face-to-face. Talking about it in
sgforums.com is a start, but it is still no substitute for a
face-to-face chat. If you're still schooling, you may want to
approach a teacher.... ask for a referral to a counsellor.
If you're working, try a counselling hotline or
something.....
You're right to say that you should get to the root of the problem.
The counsellors may not always be able to solve the problems, but
I'm sure they can give some very useful advice.
