Welcome to PC Purple Prince,
I understand the frustration and the mixed bag of goodies that come with this situation, I've been there not too long ago myself.
I don't know exactly what will work for you specifically, however I can say that you will alomst go through something similar to a grieving process if she is set in her ways.
If you know for a fact that this is not reversible, then you need to start working around the obstacles in your head to try and find a way out. I'm not going to lie, it may well be a very, very long process for yourself.
How long had you been going out with her for ?
As Mrs Bee quite rightly says, If she doesn't have the feelings anymore then there's nothing you can realistically do.

The best I can advise right now is to try and look after yourself, YOU are number one in your life, I know you'll say that she is/was your life, however you need to be selfish and you deserve to be kind to yourself. Like myself you self harm, and I would try and nip it in the bud now. Do you have a history of self harm ?

I can't tell you how to go around making progress inside yourself, only you know how to do that. Although I'm not a religious person myself, could you find a priest, rabbi, monk, elder or just a councillor who you could take your feelings to and speak with ?

Congrats on making the step to coming here and sharing your experience, it may be daunting, feel free to express yourself while your here, this is a safe community.