The sexual impulse is sadly very strong, which is why we put so many gedarim around these matters, with shmiras haenayim, shmiras negiah, etc.
I can only imagine the pain of dealing with this situation.
I posted a while back about knowing about illness in a situation involving an ex, and I am glad I did what a poseq told me and reported it to family members.
Healing and forgiveness will take a while, but this seems like someone who cannot control his te’evos. People with addictions are neurologically-damaged to an extent. Much research has been done on brain abnormalities in people with impulsivity issues.
The temptation of dirty images and websites is very strong and it is a yetzer that burns with rage and fury, r”‘l.