Husband and private browsing!!

So I've noticed several times that my husband gets up a little earlier to shower. And I usually wake up cuz I have to go pee. Well several times I've checked his phone and I noticed he goes on private browsing and when he's done with the shower he's off private browsing. We have both agreed that watching porn is not healthy for our relationship but I feel he is still watching it. Should I ask him about it or just keep it to my self. (We had problems with porn in the past so that's why our rule is no porn when we are alone. Any suggestions????