regulus

You and Regulus had broken up two months ago, by his decision, as you are both from Slytherin, you saw each other every day, but you had to act as if nothing had happened between you two, Regulus in short started a relationship with a girl from the same house, until you started to feel dizzy and vomited constantly, you thought the worst and after a blood test, it came out positive.

You were in your room, and you knew that the baby's father was obviously regulus, since they had been in a relationship for two years and had had... aha many times.
You didn't know how to tell him, since you were in sixth grade and you both had plans to leave Horgwarts.