Thank you all for your replies, guess I need all your opinions, even if they're not what I want to hear! I do love my husband, and he is a good man when he's not drinking. We get along fine day to day with all the mundane things, but it's more like flatmates would, rather than as a loving couple. I have a teenage daughter and I don't want to leave my husband, I just wish he would turn back in to the man he was before the drinking got in the way. And I've really really tried to help him with his alcohol problem but he won't accept any help, or see anyone about it. He's great with my daughter most of the time, and I cover for him when he's not. I really hope he will eventually get help and turn back in to the man I married and my feelings for him come back so we can be a proper couple again.
I really don't know what is going to happen in our future. I keep telling myself that if we can get through the next few years til my daughter has gone to university the by then things will be better or the relationship will be over. But maybe I'm just burying my head in the sand.
My lover genuinely is in an unhappy marriage, I've known him for a very long time and know how difficult his situation is. He's got kids too, his son is the same age as my daughter, that's how we first met and became friends, and he stays in his marriage purely for his kids. If I was single, we'd still be together as we are now, we've both always been clear about that. In the future, who knows, but that seems a very long way away at the moment.
I'd hate for my husband to find out, and I know there is always that risk, but I kind of feel it's a risk worth taking as at least with my life the way it is, my husband is happy, my daughters life isn't disrupted, and my friend helps me and makes me happy when he can. Without him life would be empty and very lonely. Aren't I entitled to a little bit of happiness some of the time?