Identity crisis-split personality

Well i do have an identity crisis out here, and it happens many a times..when i know that this is not how i usually would have reacted, or was that me, or i know i am not feeling what i just said.Sometimes we either underplay or overplay, why do we do that i fail to understand..we are all split personalities.and the moment i know it ,it gets all the more worse.i want to believe in astrology, astronomy,fate,stars, chemicals inside my head and pitiutary gland blah blah..aren't these all responsible to make me feel, say,do things the way i do.or else what is it?
At one shot I am shy,kind hearted,honest..and at the same time i am confident,suspicious,short tempered,unaccepting..how is it possible to have contrasting traits..in a certain scenario u r shy and suddenly some other situation u r super confident. Somewhere you r so kind and softspoken and other place you are shouting, yelling and abusive..that's what i am and i feel caught, entangled in my split personalities, trying to become the positive , but feeling negative..and just not knowing where to go..all the best to those who know me..coz they r in for some split-trouble..