I'm an overbearing mother

I watch myself doing it but it's bigger than me... I have a hard time letting anyone else soothe her, change her, even hold her without being right beside him or her... Sometimes I want to tell my step kids to move away from her even...  For no reason! They are just loving her, but I get so overprotective and just want her all to myself. I know that isn't good for her but I have a hard time controlling myself. I'm alienating myself and my daughter from her dad and I just don't know how to curb this. She's 4 months old. How do I deal with these intense emotions?