Failure in life, love - EVERYTHING

Where to begin. I am lost and very much in pain. I have found myself spinning into a black hole of depression. I have a little girl that thinks the world of me and still I cannot see past all the imperfections of my life. I have been involved with a married man for 3 years and it has brought me to my knees. This man never ever has fullfilled his promises. He has been too interested in his own PERFECT life to really let us into it. Promises made - Promises broken! All the while I have believed him, and not myself. Who do you trust? I have many times wanted to kill myself. Knowing that this would only satisfy him and hurt and destroy all the people that TRULY DO Love me. I have hurt the people that love me, all to keep this person in my life. WHY WHY WHY? This is the million dollar question. I have become somewhat of a leper in my own mind. Cannot struggle anymore with this. Don't want to turn it over - because I probably deserve it! I knew what I was doing - but I did it anyway. What a complete and utter fool I have been. I want so badly to get out of this! I don't know how. I have and continue to live in sin. I have destroyed all that I was. For What? LOVE????? Please- thats Love? I would not know it if it knocked me in the face. Have no feeling now. dont trust anyone.....ever. I once knew that I was good......but, that is all a part of my past, I once knew what it felt like to have a little happiness, that too is gone now. I once was the person that everyone enjoyed being with, that too is gone. I am a liability, I am not worth the skin i am in. I want this to stop, I want to be forgotten, like I never was born. If this is all there is, I DON'T WANT IT!!!!!!!!