Im different from the other girls he dated

My BF and I have been dating for almost a yr now and we were talking last night about something his friend stated. Apparently I am the first plus size girl he has ever dated. Which that's not the part that bothers me, it's the fact that he use to treat big girls pretty bad. His friends are like really shocked and you hear their little comments. Which I found out on my own. He's the best boyfriend I've had so far he treat me like a queen. so why do I feel some type of way about it