Harry- You broke up with Seamus because it just didn't work out. You still remained really good friends though- Seamus still likes you ALOT.

Ron- You broke up with Oliver because he was older and you were separated for a long time when he eventually left Hogwarts/ It took you a long time to get over.

Hermione- You broke up with Draco because he kept being mean to the other Griffindors and he kept calling Luna "Loony Lovegood."
You broke up with Dean because you were his side-chick when he was with Ginny and you had NO IDEA that he was going out with Ginny. You told her and you both dumped him. You never loved him anyway.

Draco- Blaise and Marcus were both VERY abusive towards you. Hitting you, screaming at you, casting crucio on you, flirting with other girls and being nice to you when you were with other people. Then Draco practically saved you. When he gave you that note, you thought he was gonna be the same as Blaise and Marcus considering they were all friends.

Fred- Cormac was just a classic dickhead. Nothing more. And Neville was just...a phase. You got Neville because you wanted Fred's attention (Neville was in on the plan). So you weren't technically 'exes.'

George- Cedric died so....yeah :( . And In your second year, you had Tom Riddle's diary and you kept on meeting him. He told you he really liked you and to keep him and you a secret. He was just using you. Ginny was sworn to secrecy. She feels really bad since she bought you into this. You could've died.