How to tell my parents?

I just turned 18 and he just turned 20. My parents are very strict as in no real alone time with guys but somehow i screwed up and found a way around it. Now i'm 4 or so weeks pregnant and i don't know how to tell my parents. Dad always told me he would kill me if he found out i even touched a guy. I don't know how to tell them without losing my dad's respect or most importantly, losing his heart. Please help, i'm terrified. I know we screwed up but everyone sins. I just want to be forgiven and then i need help/advice. this is a scary time. any thoughts?