Do you have emotions? Do you show them?

I can feel deeply and show nothing. My friend once said that I never show stress, fear, or depression. (I know I show anger.) I have huge difficulties dealing with stress, but somehow (and I don't know how), I don't let on. I'm seldom scared, and it's usually not when other people are scared, anyway. I used to be very depressed, and no one else knew. They couldn't figure it out, either. As for the aforementioned friend, we do spend a lot of time together, so I was surprised she didn't notice my varying emotions. I just don't show them. Is anyone else like this?