What do YOU think? I could really use some good advice!?

My boyfriend and I have been dating for almost 8 years now. We've had our ups and downs like every relationship - sometimes we have a blast together and sometimes we dislike each other. I've currently run into a situation regarding my relationship and I'm having a difficult time making a decision and could really use some good advice...Some important background information is necessary. So about five years ago or three years into the relationship, I found inappropriate conversations and e-mails trying to meet up with people that he had met in online chat rooms. I confronted him, multiple times, about all the things I found and he denied it was him at first, and then he promised never to do it again. He told me it was an outlet in which he could be himself without being judged. Ok, his mistake, maybe he had a hard time opening up intimately – I understand it’s difficult to trust people in that way. I know he loved me and would never actually go through with it, so I took his word and moved on.Fast-forward to present time - eight years into our relationship or five years since the previously discussed scandal. I found him searching craigslist erotic services for all types of shit - men, women, trannies, orgies, etc. He's even gone so far as to respond to a few ads while I was at work seeing if he could meet up with these people. I don't have any evidence implying that he's actually met up with anyone or not. I’ve been monitoring his actions for the past few months and he’s still browsing every once in a while. I know I have to confront him, but I feel like I need more hard evidence so he can’t lie to my face. I also feel like I need more hard evidence to justify my leaving the relationships. I’m just not sure what evidence I am looking for or when I’ll get enough evidence to make a decision.I've tried to get him to talk about any possible fantasies he might have and try to get him to open up sexually to me, but he never mentions any crazy things he wants to try. I mean, we probably have as much sex as every other healthy couple, so it's not like he's deprived. He JUST recently (in the past six months or so) opened up and started talking about masturbating, but only because I pressed the issue.I am furious and upset and am not sure what to do. I know the easy answer is to leave him, but I feel like I've invested so much time and energy into this relationship. I know he has issues with poor self esteem so I kind of feel bad just leaving without trying to work through this with him. I feel like I owe it to him to try and help him through his issues. How do I determine if I should leave it or try to save it? I just don’t think there’s any trust left. I just feel like I gave him a second chance before – if I give him another chance this time, who’s to say he won’t do it again?

my friend dated someone for a long time, maybe 5 or so years and then he finally told her he was way into s and m and had been interested it since he was a young boy. that is just an example but this guy sounds as if has some type of compulsion for weird sex. make sure he wears a rubber....