Do you know this song?

It goes something like.... There's a single mom thats barely getting by on waitress pay and there's a fireman that buys his morning coffee there everyday he's about to pop the question and she's gonna say yes they just dont know it yet... and another part goes.... in nine months from now they'll be rocking baby Beth they just dont know it yet.... thats all i know and I know the songs name isnt "they just dont know it yet" i tried it and came up with nothing.... please help!