Block boyfriend's internet...?

Well I've been with my boyfriend for a year and a half, and I constantly caught him looking at naked girls over the internet, he did it so many times that I became really insecure, he doesn't have internet on his laptop so he would do this through his phone, we are on the same phone plan with the same account, so am bale to block his internet, I would feel childish by doing this, but honestly, I feel like insecure about it and feel like he might do that again..I KNOW IT SOUNDS CHILDISH