When is porn a problem?

I've noticed my bf watches porn daily and masturbates daily. We share some devices and it's always in the browser history. Every day when he gets off work he comes home and does the thing! I honestly find it disturbing that that is his routine. I know it affects his sexual performance and our sexual relationship, because he can't get aroused as easily. What I'm wondering is when does it become a problem? I've already told him how I feel about it, and that just makes him try to hide it more. I'd love opinions, as this is not anything id bring up to family and friends!