Butterfly,
I felt a lot like you do! My STBXAH took a shot at sobriety but eventually gave up. He had told me over and over how much he loved me and didn't want to lose me. But eventually the alcohol and drugs won and I became the enemy. He walked out on me, leaving me with the sinking ship. He appeared to do so without a care in the world for me and my well being.
Now, close to 1.5 years later, his life has completely fallen apart and he wants me back. It is so obvious that he just wants to use me but my heart still wants to believe he loves me.
I am not going back with him. The trust is gone yet I still feel sorry for him at times. I still get the urge to want to rescue him but then I remember all the pain he caused.me and change my thinking. That took practice! You will get there. It just takes time and practice!! Be kind to yourself and get healthy because I wouldn't be surprised when his life starts to unravel and it will, he will suddenly be the most sorry and loving man again....until he wins you back!!