I think I already have a fair idea of the type of responses I will get to this post. I'm really looking for people to help me make sure I've thought of everything before I decide what to do next.
Story is this - been with DP for 2 years, recently moved in together along with my 3 young children. He has some form for being shit at communication - he clams up, gets defensive and sulks. Despite this, it has been a good, healthy and happy relationship. I have had very little to complain about.
We have had the best, most exciting sex life I have ever experienced. My marriage was the stark opposite in terms of no sex whatsoever. DP is sexually very adventurous, me far less so but we have always talked very openly about sex, about the things we'd like to do and try and the things that we fantasised about but didn't think would become a reality. One of these things was involving others -partner swapping,dogging, that kind of thing.
DP has been very open about the fact he gets turned on at the thought of us being watched having sex but has always maintained that it was a fantasy that we wouldn't act on. All well and good I thought.
Until yesterday when I stumbled upon his open email account on my laptop and realised he was registered with a partner swapping website. I was able to access his profile and it seems that he set up a 'couples' profile saying that he and I are looking for other couples and singles to have sex with. he has not included photos of us together but has posted photos and videos of him wanking (just his cock, he's not identifiable). I could see that he had sent dozens of speculative (hi there type) messages to people and several asking for photos of women's tits.
Most worringly, he has had an online chat with a man who describes himself as bisexual who he gave his number to after suggesting a couple of dates to meet. He told this man he wanted him to fuck him.
His activity on the site stopped about 3 months ago as far as I can see. However, it seems to have been at a peak in the summer, especially over a week when I was having a miscarriage. 
I confronted DP last night. His first reaction was that he is simply highly sexed (true) and that he was using this for wank fodder. When I mentioned the messages to the man mentioned above he changed tack and started saying he was doing it for a joke; to wind people up; to see how much detail he could get people to divulge. He refused to show me his mobile phone - he says that this guy text him a few times but he ignored every text.
What now? He says he loves me and knows he has been an utter dick, that he is sorry and that he wants 'us' to work. But, how can I ever trust him again? I genuinely believe he didn't meet this man for sex and my gut instinct is that he was using it as wank material. Does this make it ok though? I thought we had a fantastic, open, adventurous sex life.....clearly he thought otherwise.
Advice/comments/views would be much appreciated.