Cheating Help

I have been with my boyfriend for 3 years. I found out he cheated about 7 months ago. I love this man, and so, I decided to stay. He told me all the normal bullshit. "I promise it won't happen again, I love you, I'm sorry." This is where it gets interesting, and where I'm confused. He has not since physically cheated. Now I'm just in a porn battle. He loves boobs, he goes on tumblr to look at boobs, watches bouncing boobs on pornhub, and I recently found out, he uses Snapchat to get pictures of boobs from girls, which I was furious about!! He is seriously addicted and has made it a habit to do these things ONLY when I'm not around. He has voiced that he needs help, and wants help, that he is done hurting me. My question to you guys is, can it be helped? I've heard the, once a cheater, always a cheater, and he'll never change. But, I don't believe that, and I'm sure someone has evidence against these typical misconceptions. No negative comments please, I genuinely need help!! I want to here your testimonies, if things have gotten better, or if you didn't try.