Tell them now. You need to get prenatal care and all of that good stuff. You cant hide it too much longer. And you never know, they may be more accepting than you'd think.
When I was younger I had dated a preachers son. We had a pregnancy scare and his mom flew off the handle. Called me a ***** and all kinds of stuff. His dad (the preacher) was very calm about it all. He said if I was pregnant, that baby would be loved no matter what. He wasn't angry at all. Thankfully I wasnt pregnant (I was 17 and the boy was 16) but had I been, I know everything would have been fine.
Best of luck to you hon.
Tell them now! My grandpa is a preacher and I grew up in a very southern baptist home and was terrified to tell my family but when I did they didn't yell and weren't angry. Just disappointed because of how I was raised. The baby isn't the sin the premarital sex was, so they have no reason to be mad about the baby. I