I don't wanna turn my biggie biggie into a tiny tiny. :P

' I want...' is a correct grammer, and ' I wanna.." is incorrect. But you still can saw somewhere, that beacause it for the speak...

Many people use "I wanna" incorrectly. It is how it sounds when native speakers say "I want to" very fast. Sometimes people use "I wanna" to replace "I want", which is incorrect. "I want to" -> "I wanna" c'est comme "je veux" deviendra "j'veux" quand on le dit très rapidement. （c'est parce que sinon, il faut arrêter entre "want" et "to", pour distinguer entre les deux "t". c'est un peux moins fluide à dire. nous groupons les deux 't' et les deux mots 'want' et 'to' mélangent et créent: "wanto" qui se prononce en anglais: "wannuh ")

Use "wanna"with friends, otherwise speak/write correct English and use " I want to"

They both mean the same thing. Use wanna informally and use want formally. Personally I wouldn't use wanna ever. It make the user sound uneducated.