My ex

Ok so my ex boyfriend always talks to me about what his girlfriend does and how she treats him and always complains about her when he’s drinking. I still like him but I don’t think he knows that. All my friends and I know he’s been super down in the dumps since being with this girl. We haven’t stopped keeping in contact but I guess we were never officially dating. I don’t know what to tel him bc he asks me for advice. I don’t want to seem like a bitch and make it seem like I trying to take him away from her and I don’t want to tell him to break up with her. What do I do?