Why am I so unemotional?

For as long as I can remember, my emotions have always been quite limited. I tend to experience emotions in rare and brief increments. But I'd say that a good portion of my life is spent through a very non-emotional perspective. Don't get me wrong...sometimes it works out in my benefit, seeing that I don't have emotions that get in the way of things. But then again, I feel so empty at times; like there's a never ending void inside me.

Someone I know told me that I might be a sociopath. I don't feel like a sociopath...lol. I just don't experience emotions like the average person I guess. I very rarely cry. My idea of depression is more like feeling absolutely nothing...not even excitement. The only emotion I frequently experience is anger, irritation, and annoyance...if you would consider those emotions.

Thoughts?