I too had such feeling when I was in secondary school and to
poly. Keep wondering why were I here. Its was a time when I mostly
kept to myself, in sec sch, was very quiet in class, dun really
have much to talk to others, although I was with a big group of
friends. When we went out, if the ppl who were there are more then
4 ppl, I will be very quiet de. But slowly I moved out of the
circle. Its all part and parcel of life, you have to go through it
before you can walk out of it. Be strong 
My 2 cents worth 