It sounds like you were in love with the person you wanted him to be, not the person he actually was. He was actually an alcoholic, an addict that had serious commitment issues. You wanted him to be the "one" the "love of your life". I've been there too. Doing everything in my power to try to make someone else be the person I want them to be. If only I love and devote everything I have to him, he will see how much I love him and be my knight in shining armor and we will live happily ever after. Ive been there done that and it sucks! You loved him deeply. You did amazing things for him. However, he didn't do very much for you. Unfortunately he is unable to return that love because his first and foremost priority is his addiction and all the issues that led to his addictions. He will always be unable to be that person until he seeks serious recovery and that may never happen.
You "wanted to make him happy" "worked hard at trying to be the girlfriend he wanted you to be" but what did he do for you? Honestly, he blew you off and cheated on you. He abandoned you when you needed him most. Those are not the actions of someone who "cares about you so much..more than anyone you've ever dated". Those are actions of an addict. Selfish and self centered because that is all they can be.
True honest love involves mutual give and take. Your partner should give as much as you do and be there to support you just like you do for him. That is the realtionship you deserve! You sound like a great person with alot to offer someone. You deserve someone who recognizes that and treats you the way you deserve to be treated.
It's taken me many many years to realize this myself. I am still breaking free from a marriage in which my needs werent being met. My AH wasnt there for me either. Alanon has really helped me to be honest with myself and what I need and deserve in a relationship.
Although it's devastating and you must grieve what once was. Hugs I know how sad it is. Just keep remembering what you need and deserve matters in the relationship too! You deserve so much better. I pray you find the partner you deserve.