What is wrong with my relationship building and social skills?Why don't I like talking?

Ok, sounds like you are very conflicted about your situation. On the one hand you want to be nice to people and on the other you don't want to be bothered by the responsibility of having to be a friend. It sounds like you have a lot of self confidence and you are just more socially advanced than your peers. Making and maintaining fiendships is a task most people have difficulty with. I think you should take it up a level. Try making friends with people in the grade above yours, or with people who you would never otherwise think of being friends with, like someone who you are scared of or that is from a different background. One thing that sticks out to me is that you are not being yourself. You should not have to "try" hard to be friends with someone, it should be natural and mutually beneficial. If you just agree with people and smile and nod, that does not make you friends. Is it possible that you are just hiding yourself from others because you are afraid that people will not like you if you are your self? Ultimately bottling up your true feelings and only releasing any criticism or disagreement when it piles up and reaches the boiling point, exploding into a fight or other friendship ending event? Apparently taking about two years to reach this exploding point?