I had my last period on Dec. 18. I had intercourse the time of my ovulation. About on Jan. 11th I had a clump of white mucus and blood in the toilet. After this I had brown blood and spotting going on for 5 days or so...on Jan. 16 I got what I think is my period (and all the period symptoms), but for only two days. I've tested negative on HPT. Is there still a chance I could be pregnant?