I am about 16 weeks pregnant and have had no prenatal care, and haven't told my dad. How do I tell him?!?

I haven't had a period since September. I am getting bigger and I have taken pee test and they have all said I was pregnant! I am 18 and still in high school! I have only told one person and I just recently told her! I am so scared to tell my dad!! What are some ways to tell him?! Oh and on top of the pregnancy I don't want the dad to be involved in the babies life, and the only reason is because he denies it! Please help me!! I know I need to tell him soon cause being 4 months pregnant and have had no prenatal care is not good for the baby!! I'm lucky and don't have morning sickness, but all the females in my family didn't have it!! But just please help me!! Thanks!!!