Why?

I hear your laugh
trying to be with her
I hear your voice
trying to impress her
It makes me so sad to see
you looking at her 
instead of me
sitting in the back of the classroom
as if to sit with your friends
but you only have eyes for her
I have my heart in a sling
waiting for it to mend
but it has been broken for so long now
I don't think it will ever heal
words can cut deep as knives
misery can cause you to be blinded by pain
Depression can suck all the color out of life
stuck in a black and white canvas
waiting for my broken heart to heal
that gaping hole in my chest
the one that will never stop bleeding
If you cause me so much pain
why do I still want you?