I’m so sorry for your pain. It sounds like you’re waiting for her to come back or to talk to you, and that wait, itself, is almost like a separate painful experience. I think that if you can find a way to stop waiting, and to accept the break up, and start nurturing yourself by getting out there and enjoying friends and family, volunteering, walking in nature, going to the movies, going to the gym — you’ll feel better.
For future, when you get involved with someone who is committed to another man, you’re not giving yourself great odds of her being yours and only yours. Even is she told you that she was yours — you have to realize she’s taken vows saying the same thing, to her husband.
Again, I’m so sorry for your pain, and I hope you’ll use the opportunity that this break up has provided, to make a change in your life and really take good care of yourself! Let me know if you have any other questions.