I'm struggling to word what I want to say so it doesn't sound too harsh OP and I genuinely don't mean to be harsh, you made a mistake and I'm the last person to judge you for it. Having said that I read your post and saw it more from your bf's point of view for some reason, here's my take on it fwiw.
I think finding you were on pof hurt him more than you realise and him saying he didn't love you was a result of brooding on it and wanting to hurt you back. It sounds like he knew that would be worse for you to hear than not trusting you etc. Not his finest hour but it's understandable he felt like that. What he said about joining up himself and how that made him realise he only wants you has the ring of truth about it to me, if he just wanted sex it's not hard to find on there.
I don't think you're being fair focusing on what he said about not loving you, you were in the wrong here and it feels a bit like you're deflecting attention away from that and thinking too much about how much that hurt you. It's his hurt you need to be thinking about because it was you who started this whole chain of events.
That's what I'd want to see in his shoes, you taking full responsibility for what you did and for all the repercussions, including him saying hurtful things to you. He needs to see that you understand what you did to him and that you're willing to do whatever it takes to rebuild his trust in you and that means putting your own feelings on one side and focusing on his.
I really hope this post comes over the way I mean it to, funnily enough I understand more than you know about feeling lonely and isolated and that you can't talk to him about it because he's working hard for your family, that pretty much sums up my life! I wish you'd found this place before pof, it's the only thing that keeps me sane somedays 
So it's not that I don't see your point of view, and there's definitely a conversation to be had in the coming weeks about how you ended up here and what you can both do to improve your relationship, I just think you need to really own what you did first and that means putting your own feelings on one side for now.