been there done that
hiroki,
You're not stupid at all, just the opposite (no exaggerration).
I was suicidally depressed for 51 years (dysfunctional family, bad childhood), but 2 years ago, I became the last living member of my family. I then learned to live for myself, I learned who and what kind of person I am (established my own identity) and learned to believe in myself. I also learned that I have the right to do things for the most important person in the world...MYSELF. The way you write, speak, and think is profound. You know the world of feelings/warmth (otherwise, you wouldn't be able to express, feel, and think what you wrote). Explore your interests in life (they are many). Do things that you have always been interested in (do things for YOU). Then you will not only start to feel more of a sense of accomplishment, you will be giving recognition to SELF, and you will realize that life is YOURS to be happy with (you don't have to live up to OTHER people's standards, you have to simply be happy/content with what you want to do).
Do things or discover whatever you have an interest in, it doesn't have to make sense or be practical in any other way than simply to PLEASE YOU. Look at the "giant's causeway" stones (they're interesting, there's no practical reason to know about them except that THEY'RE INTERESTING to YOU). Start doings that make you happy and recognize SELF.
http://www.northantrim.com/causeway_stones.htm
Check out all these websites (why???, because you might be interested in them, no other reason).
http://www.sfmuseum.org/chin/foot.html
http://www.laesieworks.com/ifo/index-all.html#lib
http://www.ordena.com/digg/sinkhole.html
Explore Curezone and find/discover many things things you are interested in.
//www.curezone.org/forums/a.asp?q=4
I suffered a broken heart continuously over and over for 51 years (that's the way it happens sometimes, I had the headaches too from all the intense stress), but you just have to discard the past, let it go, and live the present. Once you start acknowledging your interests, things will get better.