Quick question to those in relationships

Hey guys so I went to ECU for Halloween and my boyfriend, whom I've been with for 2 years now, and is 27 and I'm 20, didn't wanna go, never does. And he got so mad about my costumes, and I like get so creative with them and I LOVE them. Now he is mad I wore them because he thought they were too slutty, And I shouldn't be wearing them if I'm in a relationship. But I love wearing them and everyone else was dressed that way and it's not like I cheated on him. Please gimme some feedback.