This is hilarious, welcome to the wonderful world of slang.
1) That phrase is an artistic feature of the music. Timbaland deliberately used bad grammar to better capture the essence of the song. Many songs (eg Jennifer Hudson "No one gonna love you") follow the same pattern.
It should be "the way I am."
2) ....don't use it until you know the proper way. "I ain't" is slang for "I am not." It is commonly used in the USA depending on where you are at but is grammatically incorrect.