It's very sad, and of course I understand how you feel. But think of it this way: you really deserve to have someone by your side who cares for you and is willing to deal with your problems, not because she has to, but because she wants to. And the fact is, that some people just can't handle difficulties long term, which is OK, because we are human beings, and each one of us have our own personalities and limits. You deserve to find someone more suitable for you, and she deserves to find hapiness in whatever form she has in mind.
Maybe at this point it's hard for you to understand it, but in the near future maybe you will find a way to forgive her, and most of all forgive yourself, because I know from personal experience that although we didn't ask for this desease, deep inside there are times we blame ourselves for not being as strong as we would like to be.
I trully believe that in this life everything happens for a reason, and maybe breaking up with your partner, will lead you to more hapiness, some time.
Take care, and keep smiling,