How Could You Believe Me When I Said I Love You When You Know I've Been A Liar All My Life? 
Royal Wedding (1951)

How could you believe me when I said I love you when you know I've been a liar all my life?
I've had that reputation since I was a youth.
You must have been insane to think I'd tell you the truth.

How could you believe me when I said we'd marry when you know I'd rather hang than have a wife?
I know I've said I'd make you mine, but who would know that you would go for that old line.
How could you believe me when I said I love you, when you know I've been a liar,
Nothing but a liar, all my dog-gone cheatin' life.

   
Girl:  You said you would love me long, and never would do me wrong. And faithful you'd always be,
   
Boy: oh, baby, you must be loony to trust a lower than two timer like me.
   
Girl:  You said I'd have ev'rything, a beautiful diamond ring, a bungalow by the sea.
    
Boy:  You really naive to ever believe full of baloney phoney like me.

Girl:  Say! How about the time you went to Indiana,
Boy:  I was lyin' I was down in Alabam!
Girl:  You said you had some business you had to complete.
Boy:  What I was doin' I would be a cad to repeat.
Girl:  What about the evenings you were with your mother
Boy:  I was romping with another honey lamb.
Girl:  To think you swore our love was real,
Boy:  But, baby, let us not forget, that I'm a heel.

How could you believe me when I said I love you, when you know I've been a liar,
Nothing but a liar, all my no good good for nothin'  life.