When two becomes Three

They say it makes the world go round,
But the opposite is what I found,
If its writen in the stars,
and its really meant to be,
me for you and you for me,
then why does it all go wrong,
when 2 turns into 3,
why are you with her,
when you are meant to be with me?

Why say you love me,
when you know it is not true,
because there is no longer me and you.

Joyous laughter,
eternal bliss,
your sweet favoured kiss,
you now share that with number 3,
no longer thinking of you and me....