Should I leave my boyfriend based on his internet behavior?

I started dating a guy a little over two years ago. Within 6 or 7 months of our relationship, I found out that he was posting ads on Craigslist under the guise that he was a professional photographer wanting to take nude photos of women. Keep in mind HE IS NOT A PHOTOGRAPHER. He claims that 3 women responded, but only one agreed to it. He also claims that he never did it. Throughout the next year I found out that he was soliciting his female friends on facebook under the guise that he wanted to do a professional portfolio. Eventually he went into counseling after he was caught on Chat Roulette attempting to play truth or dare with a young girl. He's been in counseling this whole time and he has changed. The soliciting stopped, he began to open up and we started to become very open and close to one another. This past weekend, however, I discovered that he was doing internet searches on topics such as "how to make women notice you", "how to flirt while taken", & " how to pick up women in hotel bars". I'm really tired of all of this. He claims he never intended to act on it, that it was just harmless searches based on stuff he saw on tv. Given his past history, I'm not so sure. I'm at a point where I feel like I need to decide what's best for me. Yes, I love him. I stuck by him because he went to counseling and really started working on himself. He has asked me this time to support him through this. He's asked that I understand that so much of his life revolved around using the internet for solicitation/pornography/dating, that it's a hard addiction to break. He constantly says he loves me and only wants me and has even brought up marriage. However, I'm concerned that he is prone to cheating and couldn't even begin to think of marrying him right now. I'm not sure what to do at this point. I feel like I've done my best to love him and support him, but I'm tired of feeling hurt. His behavior over the past 2 years has seriously effected my self esteem. No matter how hard I try to move past it all, something always comes up and makes me second guess our relationship. Please share your advice with me, whether is should I break up with him or how to break up with him or even how to get back to feeling good about myself. I'd truly appreciate it.