I don't like people touching me sometimes, why is that? i'm trying to change my introverted behavior.

How close you want : To be to other people is up to you. It varies from person to person and depends on how you feel about your relationship to them. There are different levels of touch. We all have different levels of comfort with shaking hands , a tap on the shoulder or a hug from a stranger, acquaintance, friend or family member. If you are concerned that it is more serious talk to a therapist.