The first day of my last period was 11th August. I had sex on the 6th and 11th of September. I took a blood test on the 19th September which gave me a level of 1.2 hcg. (Also the thyroid test came normal too.) I took another hpt on the 29th which also came back negative. I haven't had my periods till today (11th October). Is there any chance that I could be pregnant? What other things could cause such a late period?