Caught husband cheating

Long story short me and My Husband have been separated since December. Off and on trying to work things out. I knew this time our marriage was over for sure he was acting strange and I just knew. However he has still been trying to get back with me I’m pretty sure because he wants to see his daughter who I am keeping from him because he has a drug problem and he makes really bad decisions and I have to make sure that she is safe that is my main concern right now. Well I got a message from a girl asking if we were still married and I thought it was kind of strange she went on to tell me that she was talking to My Husband which I really didn’t mind because I knew we were through but I thought it was strange because he’s been trying to get back with me. She sent me the message screenshots of their convo and in the conversation he mentions how he’s doing coke and basically invites her to do it with him. Thankfully the girl was cooperative with me and now I have proof that he’s doing drugs If he wants to go to court I can take it with me. But I just think this is so crazy that people can be this fake.