Hello Elsa,
It is so sad to hear what you are going through. My girlfriend of 10 years left me for another guy a month after my mother (whom lived with us) passed away, so although my pain is not even a fraction of what you are feeling, I could relate to the feeling of having the person you love and trust abandon you when you absolutely need them the most. I hope you can find the strength you need to face the challenges you have ahead of you, and I hope you can keep faith that there is happiness awaiting you in the future. As far as your break-up goes, there is a resource I would like to recommend to you that has greatly helped me in dealing with my own break-up. It is a course that will guide you through recovering from a heart break, I am in no way, shape, or form affiliated with this course other than having gone through it myself. I don’t know if I am allowed to post a link here, but you can find it pretty easily by googling the name Eddie Corbano. It has great advise and a forum filled with wonderful people that can help you through your pain. I wish you the best of luck and strength in your fight against cancer.