"fat" days

Did you ever wonder why we have "fat" days? I mean - take today for example. I'm having a "fat" day (I just feel like I'm fat today - bloated, overweight). Yet, I'm wearing my new size 8 pants (from Old Navy) and I tried on (and bought) a pair of size 9/10 pants at the store today. So obviously I haven't gained back weight. My shirt's not tight, nothing's really different, yet I feel like crap. Is this a woman thing? I know that this sometimes happens during my period (that yucky bloated feeling) so maybe this is related to yesterday's ordeal. But I always thought that it was hormonal more than anything. Who knows? Couldn't someone invent some sort of pill to deal with "fat" days? LOL!