Can you be pregnant and still have a period without clots?

Appreciate your responses and if anyone has had the similar situation. I missed my period for three weeks and 5 days and just when I was thinking I could be pregnant... I got some bleeding for 3-4 days.. No clots though..

However I still feel a light ache in my left ovary and a presence inside...

Too scared.. What could it be.. Could it be PCOS etc..