Teacher's Secret Baby - This Secret Baby, #6

She is staying at her grandma's beach house for the summer before her senior year in high school. A couple months before she has to go back to school for her senior year, she has a 1 nightstand with a guy named Michael that was there with his friends for a weekend. He was nice and in his late twenties and she had recently turned 18 so she thought why not. 2 months later she is back at her parents and about to start her senior year in high school.
She goes to her first class and her math teacher is Michael. They are both stunned but wait until after class to talk and both decide it won't happen again. Problem is, she is pregnant.