help?! how to tell my parents?

I'm 19 and just found out I'm pregnant two days ago. I don't know how it happened because we were using protection. I'm super nervous about telling my parents. I'm afraid my dad will be most disappointed and it hurts me that I would let him down. I'm also not sure how to tell my boyfriend either. he's talked about having kids young, but I don't think he meant now. what should I say to them?!