when to tell

I haven't told my dad yet that I'm pregnant. He doesn't like my boyfriend and doesn't approve of our situation of being together and living together but he's accepted it I guess. I've been scared to tell him but my bfs already told his family and only my mom and our friends know I feel I should tell my dad. I just don't know when since I had to go in a week early for my first visit because of some complications and they found that the baby's heartrate is low and I'm at high risk of miscarriage. So I have to go back next week to get checked again. But also the problem my step mom called me a little bit ago saying my dads been upset that everyone calls him just because they want something and he calls people to actually talk and see how they are. And we had talked about me coming to see him(he lives in a different state)for Christmas or in the spring for spring training. So now I'm not sure I can do that being pregnant so I know he's going to be more upset about that to. I just don't know how to tell him or when to tell him.