Hi Short!
I am sorry you are going through so much pain. I know how hard a break up can be, especially when you were considering marriage to this person.
As far as how to keep your mind off of it? Well what works for me is keeping busy. I don't mean that you should totally neglect the fact that you are hurting, but acknowledge your pain, cry if you need to, and surround yourself with things/people who comfort you. Talking about your pain also helps alot! (So it's good that you posted here

).
I also know what you mean when you say you are hurting so badly and he doesn't seem to care. Well, this used to puzzle me to no end, until my boyfriend and other male friends explained it to me. They said that guys just react differently. It doesn't mean they aren't in pain and hurting too or that they don't care about you or the relationship, they just do not express their feelings as we females do. Guys tend to work out their pain in a different way, (although I do know some guys who are not afraid to cry and say they are hurting, I guess it depends on the guy.) I think it has to do alot with the way guys and girls are raised also, a lot of boys are told they "have to be a man" and not cry or show emotion. (I totally disagree with this!)
Anyway, I hope this helps somewhat, everyone has to find their own way when it comes to overcoming heartbreak. I know you will find your way, just take your time, give yourself plenty of healing space and know that as time goes by things will get easier!
Love,
Sujin