I feel heartless but dont want to be?

Everytime I get into a relationship I become the most selfish person and heartless to their other emotional needs besides ones that relate to just me and him. For instance now I am engaged to a man and I love him and like seeing him happy if the happiness is shared with me directly. He likes playing sofball and I hate it so I make it no secret to him that I dislike it. He asks me to come cuz he wants me to support him and I tell him in all honesty that I don't want to. And I hate myself for it because I know it dissapoints him. To make it worse his grandpa, who I've never met and never wanted to, just had a stroke and is dying. I got upset because he had to go out of town abruptly to go see him. When he told me this I acted like it was no big deal and I didn't care. He asked if I was mad and I told him honestly that I was a little. I understand that he has a heart and I don't so he of course did the right thing and went to go with his family. I was so selfish because that meant that our quiet sunday with our kids was interrupted. Even tho I know there's plenty of days to come I was mad that something unexpected happened. I didn't even care that his grandpa was dying. I don't know why I can't be considerate of other peoples feelings in those aspects. I'm selfish and I hate it. I feel like if I console people during hard times that aren't related to me directly ill sound cheesy and lame. I just feel like most of the time if its something not related to me than its none of my concern. Yes he's my fiancee but we are all still individuals. I'm not empathetic I can't feel other peoples sadness or pain. How can I get past this blockade and give my little heart completely to those I care for. It seems the only person I really only feel is my son. I'd give up anything for my son. I'd sacrifice myself for my son if need be. How can I feel that way for the man I love?