Unfaithful husband

My husband and i have been together for 9 years, we started dating at 15 and 16 and got married at 18 and 19, we now have two beautiful sons together 4 year old and 3 week old, throughout our whole relationship he has been caught several times looking at other girls that he knows every single day several timez he would search for them this went on for years i finally caught him and he promised he would stop, he started dipping behind my back and hid that from me untill i caught him he lied toy face and said he didn't dip then later admitted it and promised he'd change, then a few months later i find out that he had been watching half dressed girls on his phone on *** everyday several times a day for almost a year he even watched the videos while at work he even admitted it's like a addiction to look at pretty girls this makes me feel so little and like i can't trust him he swears he is changing now but where do i ever start to trust him and would you stay in the marriage or leave and do you consider this cheating