TMI- uterine lining

I always have heavy periods and I am used to the bloody chunks shedding but it's the day before my period and when I pee chunks fall into the toilet, some were pink and some were white. I've been having cramps and have been vomitting (constipated) but still no bleeding. I don't have a yeast infection. Does anyone know what this is? Or experience this? I'm hoping it's just maybe my uterus shedding for my cycle but I've never had it look white or pink and never BEFORE the bleeding, only after. Thanks!