inside vs. outside

In my head I'm a pretty cynical, critical person. Things flash through my mind that make me a bit ashamed of how judgmental and negative I can be. Sometimes (often when tired or hungry), that cynical cranky person gets verbalized. I'm short with people, unwilling to stop and try to listen to their ideas. and basically steamroll over anyone who gets in the way of my leaving the upsetting situation. (which usually means trying to get classmates to stop talking so we can leave and I can eat a snack and stop being hangry) I feel bad about it after, but whenever I apologize I'm met with these reactions of disbelief. I guess even when I'm being what feels like borderline rude in my frustrated resentfulness, people don't see it as upset? Several times this month, from a bunch of different people, the reaction to my apology has been laughter, or denial that there was anything to apologize for. On the one hand, I'm glad that people don't think I'm an evil bitchy person who's always angry - a lot of my self-conception and ego rests on being a "good" person. On the other hand, I'm a little concerned that even when I think my emotions are pretty evident, they aren't being communicated at all.