Disturbing or not?

I'm ten weeks pregnant and just found out my now ex boyfriend was cheating on me with a 17 year old little girl and knows she's 17! Fine with it. Mind you he's 29! Is it just me or is this somewhat disturbing? I have 2 lil girls from a different relationship and I don't and won't feel comfortable with him being in their lives anymore. And he has 2 daughters! It just baffles me how he can condone this.