Thanks innerstrength, it helps to 'talk' 
Yes, we've discussed it all time and time again. We looked in to counselling last time but it was looking to be about £500 - money we would desperatley need if we were going to be going our separate ways.
TBH I'm not even sure I want counselling - I've come to realise that we can never be what the other wants. It's not just behaviour that needs to change but attitudes and feelings. My feelings of discontent are built upon the fact that he has never loved me back the way that I loved him to begin with. It's so fundamental I don't believe any amount of counselling will change that.
In fact, we've both changed our behaviours in the past but we repeatedly end up back in this state despite the changes. We're both so tired from this destructive cycle and I feel that counselling would just be an expensive way of protracting yet more cycles of the same.
I really just don't like him any more and I'm certain he feels the same way about me however neither of us wants to be responsible for breaking apart the family.
Really, I think my mind is made up that I don't want to be with him anymore. He's always been the one wanting to stick it out but this is down to the fact he wouldn't want the 'stigma' of separating, I really don't feel that it's becuase he wants me.
I think that's part of the reason my behaviour has deteriorated towards him - I'm subconsciously hoping he'll be the one to make the decision. That admission alone makes me see what a terrible, terrible person I've become, I never used to be like this. 
Sorry for going on, I clearly needed to offload! 