Losing my sanity and becoming someone I hate

So this is gonna be a long one, but it's been eating at me for years and I have no friends to talk about it with so just need to get it out before I explode. Feel free to downvote and move on. Throwaway for http://ift.tt/2mLhC7p - 2 guys , one messed up relationship, featuring sob stories and poor decisionsHere goes...Been in a relationship with my current bf for around 10 years and typical story started off great then we moved in togetger and the novelty wore off. Stopped going out and doing things together and the sex life became almost non existent.About 5 years ago he looked through my phone I guess suspicious of what I might be up to and found nothing, because there was nothing to find and the thought of playing away hasn't even crossed my mind. Fast forward a few weeks I get the itch to check his phone, to which there were a bunch of messages to a mutual friend basically saying they wanted to get together...turns out a night we had an argument my bf went over to this guy's place at the invitation of "helping him find a bottle of wine. To this day he claims nothing happened and as much as I've wanted to believe him I just can't, so for 5 years or so it's been in my mind that he was unfaithful.One night about a year after this, I found he was using cruising websites (I was watching YouTube on his pc and he had left the tab open... that night I went to the site and made an account he would be "into". Dick move I know, but I was paranoid at this point. Within a few hours there was a message and some flirting messages coming through, he asked to meet up and I agreed. Next day I was at work, finished at 1pm but he thought it was 5 and arranged to meet this guy at 2pm. Not sure what I planned to do if he showed but I didn't get the chance as he randomly called me around 30 mins before and confessed. He promised not to go on them anymore and I came clean about his dream guy being little old me. We were trying to restore trust after all.Over the next year or 2 there were a few lapses where he just told me about, but protested he never did anything. No big deal then.Last year he started acting really secretive with his phone which awoke the paranoid wreck in me and I decided to invade his privacy, should have been a better person and just left but hey nope, transforming into a snooping bad guy. Looking in his phone he had been using grindr, there was random grindr pics in his gallery clear to see, I couldn't handle knowing he'd been on it and possibly screwing around behind my back. So I confronted him again and same story, just on to look at guys...Not for `right now' 'discreet as his profile Indicated.All the while our sex life became completely one way, we argue then talk things out and nothing changes. Neither of us has the balls to just leave even though it's not been working for years, can count on one hand how many times we've has sex this year on one hand, and I'd still have 4 fingers free. He says his sex drive is gone, yet he uses these apps. Paranoid me just assumes the worst at this point and assumes he's been getting it elsewhere.Up until this point I've been the good guy in the story, but that all changed around 6 months ago when I made a poor decision, I decided to download grindr and see if my bf had been using it again while I was at work.Sure enough there he was, so I opted to block him and then instead of closing the app I got chatting to a guy, we ended up talking about my lifes problems and he actually listened to me. It felt nice to have someone that didn't make me feel paranoid with no self esteem.A few weeks after we started talking we decided to meet up after I finished work to hang, but it wasn't long before he kissed me, instead of turning him away I started to kiss him back and we ended up doing a little more than that, I'll spare you the details but we didn't have sex. After this happened I felt so disgusted with myself that I cheated, but at the same time part of me didn't care. We met up twice more and did the same, he's said he would like to have sex, but so far I haven't gone that far. This prob makes me a bad person and I accept that.I should have kept my morals and left him years ago, instead I've become a low life asshole. He doesn't know I've cheated on him, the cycle of arguments and broken promises continues and I don't know what to do.Thanks for reading if you made it to here