Understand one thing and that is you should never pain over someone to the measure and extent you have gone through if the other person doesn't equally pain in the same measures as you. If you allow yourself to live and suffer in this fashion you will be nothing but an object, twisted and exhausted by the environment around you.
Recognize that continually living this lifestyle will be nothing but devastating, leaving you in a place of absolute desolation and depression that is almost unbearable. Why do this to yourself? You deserve more as a human being, and you must believe.
This is not a hypothetical contemplation, but by my very own life experience. I have been there, friend, and I understand how it hurts to have a consistently sustaining void, never ceasing to torture the mental faculties and optimism of the heart. However, the more we want to fill the void by earnestly trying to put the same person back into our life the more we lose ourselves in the process.
I don't advocate logic when it comes to love and relationship too often but this is an instance where the principle no longer applies. Do take a step back and look at your life for all its potential and not it's shortcomings as you probably think that she is the only potential in your life. Allowing yourself this time to reprocess all your thoughts and relinquish all the crippling notions. The probable conclusion when you are in the rational state is she is probably not meant to be in your life. Another probable conclusion that you'll make is that she is cheating on you with another man.
Stand strong and know that this is just another life lesson. Our failures in love often become our greatest blessings, however, they are often only realized when another person shows us the contrary to everything we thought was impossible by emblazing the ember of our heart in the most essential of ways, dispelling the myths of the past that we believed to be true. That person you will eventually meet—smile.
Borealis
Be slow to fall into friendship; but when thou art in, continue firm and constant.