Business on blast

So my boyfriend and I have been dating/living together for about 7 months now, and about 2 months in, I find out his ex gf is pregnant with his baby... I immediately considered leaving him, but after all I had gotten to know, I decided to accept it and stay with him.
Several months later and I'm ridiculously stressed out, annoyed, jealous and infuriated with the whole situation. This girl CAN NOT get over the fact that their relationship is over, so since she's known she was pregnant she's been the true definition of a baby's Momma. 
She would call him nonstop from private numbers and hang up as he would answer, she would call to argue about how dead beat he is and how he is never gonna see his son and blah blah. 
I was gonna go with him to the hospital to show moral support for him, but instead he's going with his family to sit in the waiting room because apparently he's not allowed in the room.
We decided to have our own within a year, but everything is starting to drive me crazy. I love him, but I feel like another woman giving him something I can't is gonna be something I forever think about. I fee like if we have our own I'll get over it but I shouldn't be thinking that way. 
Anyone been in a similar situation?