Embarassed to be a woman

I think I had my first period when I was about 11 years old. I knew what it was and I knew what to do, I was just upset that I ruined my favorite pair of white shorts. My mother wasn't shocked, she asked if i was okay and I told her yes. A menstrual cycle is normal for a woman to have. So why is it when it is that time of the month, I am so afraid people will notice I am buying tampons? I am ashamed of this natural event that effects millions of women. Why is that? Maybe its because all of the males I have known have constantly and consistantly attributed something horrible to my period.

"She is acting up, it must be that time of the month."
"Don't mess up my seats, I know it that time of the month."
"Are you always this bitchy when your period is on?"
"If Eve had just left that apple alone, you would be cool. You know that was her curse."

My period is like some wart that sits on the end of my nose once a month. I am so embarrased by it that I try to conceal it for fear of being judged becuase of it. So as the days go on, I am learning to accept "Aunt Flo" and not be shamed by her.