How can I cope with my early twin loss?

My twin died shortly after birth (almost 20 hours) I feel so guilty! It's like my entire existence is an utter betrayal to her. Sometimes I want to seriously hurt myself, but I don't. I feel so empty. It's as if part of myself has died along with her. Like there's a void where my soul should be and it only gets bigger. I'm almost 15 and i still haven't gotten over this. I sometimes think I'm the one who should have died not her... and if not I wish I did. Can anybody help me, please?