Whenever I start my period, I hate absolutely everyone.
That's extreme, but why?
People always act differently around me when I'm on my period.
People probably aren't treating you any differently but you're likely just in a bad mood. Everyone has bad moods every once in a while, and its fine so just try to tolerate everyone until you feel better.
That's probably what's happening but I don't want to believe it.
It is, and those are the times you need to take care of yourself and have some alone time.