Not sure if this helps or not, its my own personal take, but may well be individual to me, its not for everyone
You cannot do much about where you are at this precise moment, it sounds hellish, but its because you have conditioned yourself to accept that your life will only be worth living with another sharing it. Its a sad fact but the other that you had pinned so much on, has made his own choices, for whatever reason, largely irrelevant, but clearly, he did not share the same depth of feelings, reliance and need that you have. Feeling such is not a bad thing, but can be very destructive if your clapping with one hand, if two people feel that way, its different, if only one does, its never hugely healthy, in my opinion anyway.
Moving forward you have two choices, you can either pine for what you had, and try and find it with someone else, who feels the same way as you, again, in my opinion, this will only lead to disappointment and a constant let down as you search for your 'other half' the person that completes you and makes you feel whole. You may spend the rest of your life searching for this person, never feeling whole and playing a waiting game, wasting time, energy, emotions on the never ending search, and then, even if you find this nirvana, trying to hold onto it at any cost.
or
You can accept that you will never again put yourself in a position where someone else has a hand in how you value yourself, or how good you feel, or how happy you are, or even, dare I say it, how complete you feel. You can wake up in the morning knowing that your emotions, your wellbeing, your mood depends largely on you, on what you do, or how you feel about yourself. Yes, you will be alone ,but you do not have to be lonely. Some of the loneliest people are in relationships, it does take time, years, to truly accept and embrace that feeling. You could thank your lucky stars that what has happened has happened now, and not in 10 years time, so you have time to grow as a person, find yourself, and free yourself from the shackles of dependency on another. It may be the last thing that you are considering at the moment, because like a drug addict, you need a fix, a quick fix, of love, kindness, physical touch, and it hurts to your very core, but like with any addiction, the longer you abstain, the more you will see life through different lenses, until your free. Not many people are free, most are bound to something, money, love, drugs, power, ego, pride, but if you can manage to free yourself just a little bit a day from the thing that controls you, in this case, love for your husband, you could find freedom from dependency is the happiest feeling in the world.
Free people still find love, but its a small part of who they are, not the all, and its not the hell that needing love is.
This could be the beginning of your life, and adventure to find yourself, without the submission to another, or the need for all the things that currently you pine for.
As I said, its not for everyone, you may wish to stay on the merry go round of what passes for relationships these days, and if you do, that is your choice, and I hope you find what you are looking for, but there are alternatives, and looking at the situation from a very particular angle, one could say that what has just happened could well be the best thing that has happened to you, because it has taught you that to put your happiness in someone else's hands can really hurt.
Good luck, and as people have already said, the pain does pass, the hurt passes, the pining, the sadness, but it will pass quicker if you focus on the future.