Angry at everything?

I seem to always get irritated easily, and it isn't even a period thing, it can happen any time. Mostly it occurs at work, suddenly I'm furious and really frustrated or sad, I try not to show it but I'm sure people can tell. Then a few minutes later I'll feel just fine again. And even if a customer interrupts me for a question or just stands too close I'll get pissed off and irritated inside. I don't know what's wrong with me but it is interfering with my work life and sometimes my personal life - mostly just with my parents.