I’ve had a similar issue with my boyfriend. We’re 19 and have been together for 1 1/2 years. He informed me when we were just getting together that he had a past issue I expressed him watching it kinda made me uncomfortable and he agreed to stop. I would check up on him occasionally and ask if he was still not watching and I was always informed he wasn’t. I found out about 3 days ago that wasn’t true and that he never really ever stopped watching it. And it was MUCH WORSE than I could have ever expected. I was so incredibly heart broken. He lied about it at first said it has only been 2 weeks instead of months. I know you were asking what you should do and I can only share what I did and hopefully that gives you some insight. I was very upfront with him on how it made me feel, I didn’t hold back. I wanted him to know how much his problem truly hurt me. He expressed that he was sorry and actually acknowledged my feelings and validated them knowing how much he hurt me. Since we are still in the beginning stages of fixing it we just set up boundaries I made sure he know exactly what I thought was too far and told him I couldn’t handle if he continued the way he has. I offered my help and support to try to stop and that’s the best thing I can hope for. I was also completely devastated, I had really no hope for the future, I lost so much sleep stressing and crying. You should really try to do what you feel is best. I know you want to help him but you can’t help people who don’t truly want to change.