I don't know who

The one I love has found someone else
But the part that hurts me is who
A close friend has taken her
But what should I do

It's not his fault he didn't know
He can't be blamed for my mistake
That doesn't mean when I see them
My heart doesn't want to break

But I can't hurt my friend
Because of the girl I love
Because a sin like that
I would not be proud of

Oh how this pains me
What can I do
My love or my best friend
I really don't know who