I did IUI on 22nd Dec. Pregnancy became positive. Had stomach cramps and bled (not as heavy but with few small to medium size clots) from Thurday night (2nd Feb). Bleeding is much less now and no pain. Did a scan and they say they couldn't see a sac and the HCG level on Friday was 3731 and Sunday was 1201. I know it's dropping and most likely looks like a miscarriage. I still feel there is still something growing and it was a vanishing twin that I passed with blood.Can the HCG levels drop and increase again? Was the sac not visible beacause of the tissue and blood?