Parents controlling me

I'm terrified to tell my parents I'm pregnant, I'm 10 weeks and baby will be here after I'm 18. But I know that as soon as I tell my parents they will try to take complete control over my entire life and separate me from my fiancé even though we've been engaged for a year and been with each other for two years. They're not understanding people and both my father and grandfather are preachers. My father is on anti-psychotic medication because his temper is so bad. Is there anything I can do as a seventeen year old to keep them from controlling every aspect of my life until I'm 18? Or from trying to force me to have an abortion or to give my baby up? They're very unforgiving and quick to anger. I'm scared of what they will do whenever I tell them. My due date is a month after my 18th birthday.