Single mother fighting for sole custody

I need some help on what my chances are for winning a sole custody battle. I have been the primary caregiver for my child single birth me and her father tried to work things out but didnt work cause he was always verbally abusive towards not only me but his mother which whom he lives with. After our broke up 7months ago we had agreed to joint custody with her primary living with me and acess to him on alternating weekends. Now he is trying to get sole custody under the fact that im a druggie which C.A.s did a drug test which was negative.. He is also trying to get it under the fact i cant care for her because his parents always feed her and bath her when i was at their house with them.. but that was cause his parent wouldnt let me do anything which was one of the reason why i left in the first place cause i wasnt allowed to parent my child.. Can someone tell me what my chances are that he would win against me.. Also the father has a history of drug use and is an alocholic who ditched his daughter to his parents to drink