I'm so sorry to hear about this. It scares me because I know I'm not far from where you ended up... Everytime I have relapsed I have lost something or someone very dear yet I STILL have those days where I think of a drink or a drug. Cunning, baffling and powerful, as they say.... I can't offer any advice you've likely not been given at this point, but I offer my support and just want to reach out to you and let you know that you are NOT alone. Also, as the daughter of an alcoholic father who is also trying to get sober and who also recently watched his wife (my mother) leave after 30 years all I can say is that I know your little girl loves you, like I love my dad. As an adult I am full of forgiveness and sympathy for him and I know that his demons were really eating him up all his life but he did his best and I can't fault him for most of it. At least you are still going to be in her life like my dad is in my life. And at least you are trying to beat this; its admirable that you have not given up. If my fiancée and baby boy were gone I don't know what I would do... I don't know if I would be as strong as you. I hope things get better. I know you can stay sober, especially if you did before. You know what to do.
Hugs and prayers.