Porn addiction

Hey guys so my husband has had a porn addiction since he was a teenager it has started effecting our sex life and causing problems in our marriage, he can’t even stay hard with me anymore thanks to all the porn he watches..anyways he said he’s going to stop that he doesn’t wanna ruin our marriage over it because I’m more important I wanna believe him but this has been going on for so long it really makes me wonder can he change? Can someone that’s been addicted to porn for years go without it?? What about the damage that has been done..can it be reversed? He said he’s willing to put a app on his phone so I can track his internet history and honestly until I can trust him again I’m really thinking about it..does anyone know of any free apps that track that stuff and any advice would be great for people that have went through this..