I have ummmed and errred about posting but here I go. I will try not to project my reflections on to your new relationship, you need to decide on that.
My husband and I started off as housemates. There was an instant friendship, we just got each other and made each other laugh. He especially made me laugh. However he was not remotely my type, and I did not find him physically attractive at all. I'm not actually friends with men very often, as I think I blur the lines, I will always ask myself if I fancy him or he fancies me. I probably knew that he fancied me and as time went on we were increasingly tactile, holding hands on the way back from the pub, giving each other a peck good night. I didn't take it all that seriously, I was pretty young, recently moved to a new city and in fact I had a boyfriend although long-distance and I'd got back together with him after moving so I think we both knew we were drifting apart. Eventually I made the move (he never would have) as I felt jealous when he paid another girl attention, and one thing inevitably led to another. I finished with the boyfriend and we started going out, but I blew hot and cold. I hurt him a lot at the beginning, deciding whether I wanted it or not. I moved out fairly soon as living together became too intense, but ultimately we stayed together, got married, had two amazin children, built a lovely house together.
Fast forward to now, 20 years later. Am I happy? Honestly, no. I am trying very hard to accept what I have and feel grateful because I know that I am very lucky. We still generally get on very well, we still make each other laugh. We are intimate with each other although I generally don't initiate it, but I don't push him away either and can enjoy it. The problem is that I am not physically attracted to him. I'm not turned off by him or repulsed by him, and I enjoy kissing and cuddling with him. I suppose its the old I love him but I'm not in love with him. Three years a go I got very low and I told him this. We worked through it and he did everything he could to make my life better and easier, and now I tell him I love him. I do love him. But there is something missing and every so often I wake up literally in a cold sweat and panic. I am on prozac for anxiety.
I will not leave him. We are a family and I believe in marriage being for life, especially if you've had children. I made a choice as an adult, and I have to live with it. My legacy will be giving my children a life with parents that stay together, because neither of us had that and I think it had a massive impact on our self-confidence. I know MN will tell me I should just leave him and be on my own, but life really isn't that simple, is it. Or it is, but others get hurt. My biggest regret, and guilt, is not allowing him to find someone who truely adored him and found him absolutely gorgeous, because he deserves that. I will make it my mission to treat him as he deserves.
My advice to my younger self would be to be truely honest with myself about how physically attracted I felt, and to follow my gut. There is always lust fuelled chemistry at the beginning of the relationship, but when you've been at home with a toddler and a baby all day, and you're mad as hell at your husband who's just sat down to have a cup of tea rather than walk the dog, chemistry doesn't do you any good. Friendship is most definitely the most important thing in a marriage, but there needs to be something more. I think you know if you have it. I listened to my head, telling me it was right without really listening to my heart which was telling me it didn't FEEL quite right.
I would also say that a frienship where one person has always held a candle for the other, hoping it would be more, isn't really a true friendship. I think it was always inevitable that at some point you would succumb and his passion will drive things forward for a while. He would have been hurt anyway at some point, so if you do eventually decide that what you feel isn't enough for a long-term romantic relationship, then I think you have to accept that. You will not remain friends, because it was always one sided in some respect. That is sad, but you were both wishing for different things from the beginning.
On the other hand, my experience is not everyone's experience and if you decide that what you feel is as amazing as what he is feeling then I wish you a long and happy life together, as I certainly think that's possible from a friendship. Please just don't go along with it for the wrong reasons, for him, or because you think it should work. Go with your gut because you have a long life ahead of you.