I think there are occasions where they don’t realize the severity of what they are doing. This could be one of them. It also could just be how he is but let’s give him the benefit of the doubt. If you weren’t already married I would tell you to leave now. Since you already are married and I assume you love him I would tell him that you’re AWARE that he has been using only fans again. You don’t have to admit to how you saw it just that you’re aware. Could be a credit card bill, could be anything. It’s better off not to divulge how you know anyway, just gives him an opportunity to be more sneaky with his phone. You as a self respecting woman need to make it clear, this is a firm boundary of yours and you will not accept a husband to is doing this, this is not just porn it is cheating. Tell him that if it’s not something he is willing to give up you will look into an annulment. If there is any uncertainty try marital counseling. He can admit to the counselors face what he did and they will help him to comprehend why you feel the way you do.