Are you young-ish? Have you ever lost someone important? Empathy often develops with age and experience. It's hard to care about someone losing someone if you've never lost someone important and experienced the pain of it. Also, if you are in pain, it's often hard to see past that and feel for others who are in pain. I doubt you are a terrible person....probably either depressed or inexperienced.

Edited to add: when I'm manic I can be much more self involved and less empathetic. When stable I'm overly empathic.