I Was Supposed To Start On The 12th Of December

I was supposed to start on the 12th of December and have been regular for past four months. Im 8days late and in between i kept feeling weird with sore breats and heavy abdommen area and a little nausea so i took pregnancy tests but not in the morning in th afternoon and all negative. Today i saw first orangey red stringy blood in my underwear, and then when i wiped i had slightly big clot of blood and it was red. Then it got heavier and its all stringy clots with redness. But i have cramps now. Whats going on??