"He rubbed his relationship with Lavender Brown in my face 6th year to upset me and put me in my place. To remind me HE could do better, he was settling for me and I should be grateful. Then he asked me to keep our relationship a secret. In part because he was feeding love potions to Harry and wouldn't have wanted him to know before he had his cover story ready. I believe that he has been giving Harry those potions in our 5th year before he began dating Lavender Brown. I know that he was seeing Lavender at the same time he was telling me we would be together forever, marrying someday.