I wouldn't say I lack empathy, at least in some cases. Sometimes I seem to feel others' feelings as if they were my own. Usually it's strong joy, strong pain or sadness, and strong anger. But I may not know what had brought these feelings about, and why they are there in the first place. I may not even really understand the person I am with. (One friend of mine who's known me for about eight years keeps telling me that I try to love people I can't understand and have no idea *what* is it that I love, which is just not good. She's right, I think).
More often than not, it's painful, especially when the other person is distressed. I end up just wanting to escape because I don't know how to cope. I know that one is supposed to react with feeling sympathy and wanting to help, rather than running away, but I can't always help it. There were several times when my mother was crying and I wanted to literally bang my head against the wall (otherwise I've never done this, or wanted to do this, but this is as close as I can get to describing this feeling). It was almost like anger, and I thought I'd burst out and say something really inadequate, until I realized I was simply feeling her pain and it was making me frustrated.
This sort of empathy is probably normal. I can't imagine how one could sense all the emotions that somebody else has, apart from the most basic ones; it's beyond human capacities, I think. We'd all be saints if it weren't.
What disturbs me, personally, is that I can't always respond adequately to the empathy when I have it, and get the urge to withdraw and save myself instead of staying and helping in some way (it doesn't happen always, but it's there).
It's also strange how those emotions coming from somebody often seem out of context; I don't "get" the general pattern of how somebody is feeling when talking to me, and I may not get the subtext of their words as well, so I basically may be misunderstanding more than half of what they're saying, when all of a sudden there comes this sudden outburst of emotion and I am kocked off balance. It's bewildering. I could easily imagine how somebody who has greater difficulties reading facial expressions or gestures could feel the same way and be even more confused.
Now I *loathe* it when children and animals are being hurt. Or rather, I can't bear to see it. It makes me want to beat up the person who's doing it, or worse. I don't think I'd be in control of myself if I saw something like happening before me in real time. When it comes to it, I think I'm a lot more empathetic/sympathetic towards animals than people, really.