Stress and P.M.S.

My mother once told me, and has since then continued to tell me, that stress does not exist. Hilariously, neither does P.M.S. They are both society's excuse for making excuses, if you will. My question is: how do you not get stressed trying not to be stressed? Whenever I offhandedly say that I'm stressed and she tells me that it is virtually impossible, my mind goes into a cycle similar to this: "Oh no, if I'm not stressed, then what is happening to make me so... crap! How do I explain what I'm feeling right now? Ahhh! What's going on! Why can't I say I'm stressed? Is my mom mad at me for saying I'm stressed or does she just think me a weak person? Gosh, she sure stresses me out..." *cue cycle restarting*
The same goes for P.M.S., except substitute bitchiness for the stress.
The point is, I'm going to work on not letting my mother tell me how to feel when there are apparent physical and mental indicators proving otherwise. This is a huge step. Huge. Honestly, I'm a little stressed about it right now. I'll get into that later.