caught my husband watching porn

Last night, I accidentally saw the search history on my husband's phone, and it turns out there are a lot of porn sites. He just came back from a week-long business trip. I'm really sad... I feel betrayed. Does he masturbate and fantasize about other women? It's true that my husband often initiates sexual intimacy. Maybe if we don't have sex for a week, it's quite hard for him... but still, this makes me sad and angry. But I haven't told him yet because I'm afraid I might just be overreacting. Is this normal?