Some women have implantation bleeding/spotting, which occurs around 3-6 weeks pregnant. It's when the baby is burrowing itself into the lining of the uterus, causing the uterus to bleed or spot a little. I know I had it with my 3rd child for 5 days. I thought it was a period until I decided to test anyway and I was pregnant. With my 4th it happened again at 6 days past ovulation which made me only 2 weeks pregnant. I didn't know I was pregnant until I was 3 weeks and 5 days pregnant though. I kind of figured I was though being that I had spotted for a day or so beforehand. But, if it's a miscarriage there's nothing you can do about it now. All you can do is take an HPT and see if there's any hcg in it. If so, go to the doctor or the ER and they will do a blood pregnancy test on you to see if there's any hcg left in you. If so, they might check you in a few days again just to see if the hcg is rising. If it's dropping then you're miscarrying but if it continues to rise they will say you are definitely pregnant and more than likely it was implantation bleeding. The only thing throwing me off is the passing of small clots. With implantation bleeding ,that would be very unlikely.