Boyfriend's baby mama

So my boyfriend has a child with his ex girlfriend. They took their son together to some thing and he said that they plan on doing stuff together with him more... It kinda bothers me because they aren't a family anymore. They are just co-parents so it's just weird. They just recently started this. I don't wanna be upset because she is pregnant with her current boyfriend now and it's not like he is hiding it from me and I know he loves me. Does anyone have any advice from being in a situation like this?