Can I be pregnant even though I have been bleeding?

Hi, I am very confused, I have been off contraception for 3 years and have never got pregnant I recently found out I have pollysistic ovaries, I came on my period on the 27th nov for three days but it was a light period, I am now obsessing myself thinking was it not a period and something else and could I be pregnant? I have some signs of pregnancy like extreme tiredness and slight headaches, I don't know whether I am obsessing that much I am just making myself think I'm pregnant, I have had three pregnancy tests and all three negative, I am due on my next period 27th dec , can someone help?? Thanks xx