Trust issue

Shena

Ok so I just got ingaged last month on my birthday we have been together for 18 years and have two girls 8 and 12. I'm happy in my relationship but I have a issue with him watching porn behind my back I've told him how it makes me feel and he said he would stop but I'm constantly seeing things on his phone history. I need some advice on how to deal with it and why he's doing it please let me know what anyone thinks....