Talk to Gynecologist on Miscarriage

I am covid19 positive. One week back i felt lighter pain and had bleeding after that I also got dark dry blackish clots, I went for and ultrasound, it showed my pregnancy more than 12 weeks and a heart beat of a baby too and the ultrasound was normal. After 2 days I got cramping and bleeding (it was not that heavy) pain tha bohat ziada but bearable tha. I felt like a ball came out of my vagina. (i was passing stool and urine at the same time) after that I saw such a bigger clot i haven't seen in my life. I got panic and confused as it was my first pregnancy. I again went for an ultrasound and dorctor told me that there's no pregnancy. I got so depressed that how can this happen all of sudden everything was normal 3 days back. I again went to gynae with informing that I am positive because it was an emergency. She told me the same that you're not pregnant anymore and advised me some medicine. I am still in denial that how can this happen all of sudden and what can be major reasons of a