Who is “Jack” in this scenario?

There’s a country song, and the chorus goes like.

“No, it wasn't the late-night crazy
Two in the morning up calling you, baby
I wasn't out with my friends in a real drunk crowd
That ain't at all how it all went down
It wasn't the whiskey and a country song
That you were hearing from my end of the phone
All that talk I was talking 'bout missing and wanting you back
That was all me
That wasn't Jack”

What does he mean when he says “that was all me, that wasn’t Jack”?