I'm sorry you are going through this. Welcome to SR...you will find a lot of support here. I wouldn't believe a word he says, especially since you have a daughter. Is he the father? Not that it matters...father or not, I would never allow someone doing drugs around my child.
There is no way I would ever even consider taking him back until he had at least one solid year of continuous recovery. One month isn't anywhere close to long enough. If you are even considering taking him back, don't do it until he has proven unequivocally that he has been clean and sober for at least a year.