My boyfriend masturbates in front of me

Since I started living with my boyfriend he seems to be very loosened up. I know that all guys masturbate from time to time no matter if they're in a relationship or not, but I always supposed they do it in private. For instance just the other day we were watching some sitcom and laughing when there were few scenes of one of the actresses in a bit showy clothes. He got erection and in matter of seconds unzipped himself, outed his penis, jerked it then wiped it and put it back in the trousers again. Like nothing happened. He continued laughing and commenting. Which makes me think about the fact that he always has paper tissues in the car, I once took them without him noticing it and next day there was a new box.