No offense - I mean, I dont wanna start anything.
But if you didnt wanna get pregnant, then why did you continue to have sex? That was the risk you took when you decided to "pleasure" yourself. And you need to take the responsibility and own up to it. Sure, your dad may freak, but he will get over it with time. You cant just wait until your "bigger" to go to the doctor. You really need to go now . . .
You had sex, you need to deal with the consequences. You cant hide a baby forever. The sooner you tell your dad, the better.