Nervous about husband..

My husband has a porn addiction. I used to be 100% okay with him watching it. We would watch it together and I would even send him videos sometimes if it was something I thought he would enjoy. Well, it escalated to the point that he would go "take a poop" 4 or 5 times a day, and we didn't have sex for months. He broke his smartphone and has had a flip phone for a few months now, so he hasn't been able to look. Our sex life and our relationship has been SO MUCH BETTER. I mean seriously it's a dramatic change. Well, he wants to get a smartphone again, and I am really nervous that he's going to go right back to it :( actually I KNOW he will. What do I do? He just lies and says he's not looking until I catch him again. How do I cope with this? It's like I finally have him back and now I have to give him back to his mistress :(