I cheated on the love of my life.
Are you serious? Why would you do that to someone you love?
She got sick. I felt saddened by her sickness so I turned to another woman.
Your partner gets sick so you go out and betray them by cheating on them? That's horrible! You need to admit what you did and apologize to your partner immediately.
The doctor said she doesn't have long to live. That's why I cheated on her.
If your partner is dying that makes cheating on them even worse! You need to be there for them to support them in this difficult times. They deserve to have love and support in their last remaining time on Earth.