You have a right to say who can and cannot be in your home. You don't know this chick well enough to have her staying with you and your baby. He is not willing to man up and just wants his fun. This is crazy. Like I said earlier, I'd call a locksmith, throw his shit in suitcases, and toss them outside.
The world opens up... when you do.
Oh, oh, can't you see? Love is the drug for me. ~Bryan Ferry
"Love is that condition in which another person's happiness is essential to your own." ~Robert Heinlein