Visitation rights with my kids...?

I am newly divorced and my ex wife seems to think she has a say what i do or with whom I am with while I have my weekends with my kids. My girlfriend is midway though her divorce, has a girl my oldest kids age and they get along. I want to be able to do things together. My ex doesn't like the thought of my girlfriend or her kid seeing my kids since her divorce isn't final. My girlfriends soon to be ex is an alcoholic and my ex is afraid he might har us. Does she have a say in this?