Trying to write a song that has been stuck in my head

Nah nana nana nana nah....hey, I'm not your baby
Nah nana nana nana nah....yeah, you're not my problem (anymore)
(Nah nana nana nana nah)
Boy you lost everything, when you walked out on me
yeah, you gave up the right when you said your goodbye
....and now you're sorry
Hey, hey
Nah nana nana nana nah
I'm not your baby....

It's not easier, like you thought it would be
he doesn't hold your hand through your miseries
instead of right and wrong all the lines are blurred