Boyfriends ex

So I'm 5 almost 6 weeks pregnant. My boyfriend and I talk about our baby, but then he talks about when his ex was pregnant. And then I get upset because I hate him talking about her. Tonight he told me that when she was pregnant they were as close as ever and it made me livid. I'm am now on the couch, is it bad for me to get upset? What do you guys think of this, it's not a one time thing he talks about her prenancy a lot. Sorry but I'm not her and this is a different baby.