Uneasy

Okay, so the guy I've been seeing since i was a freshman in high school (so its been about 5 years) has a baby on the way & not with me. We broke up for a few months and he had a fling with a girl and got her pregnant, they were never in a relationship it was a friends with benefits thing. We ended up getting back together. So they haven't tried being together for the baby, but shes due in just 3 weeks & its really starting to stress me out, because I'm terrified hes gonna see her & this child and feel like thats where he needs to be. We tried conceiving for so long & it never happened. Its just something that really hurts me & scares me at the same time. Do i tell him how it all makes me feel or keep it to myself?