Boyfriend, other girls

So there was a day that my boyfriend went to go hang out w his friends n I told him if there was a specific girl that I didn’t like (because of things she’s done) there than I don’t want him to go, he went anyway knowing she was gonna be there, when he went home I asked him if she was there n he said no but than after a few weeks i found out she was!! He said I was overreacting do u think I am??

Am I being unreasonable??