Boyfriend (M24) is watching an obscene amount of porn behind my (F25) back

My boyfriend (M24) has had a history of porn addiction and he now prides himself on not watching it anymore. Low and behold I find on his iPad history from just the other day he watched over 20 porn videos in one sitting. That is not healthy and it makes me think he’s acting like a horny little teenager and isn’t mature at all. It’s actually quite scary seeing that. Some of the stuff as well…

Can anyone offer their perspective or their experience of whether this is normal and how do I approach this? We’re in a long distance relationship so it scares me even more than he’s just a porn addict hiding in our relationship. How can I approach a conversation without attacking him and being supportive? If that’s even possible in this situation.