How should the characters in my story find out?

Im writing a story about the two characters Abby and Christofer, currently in my story Abby and Christofer had gone to a club and abby got drunk, they slept together. Now I want abby and christofer to find out that abby is pregnant, but how should they find out?When? What should happen, should her parents kick her out??? Please help Im having writers block