Hi, I Had Unprotected Intercourse On July 27, 2016. Next

Hi, I had unprotected intercourse on July 27, 2016. Next day I took one I-pill and another one the following day. So I took two I-pill as I was scared. My periods arrived on August 10 as per my usual period date without any delay. I usually bleed for 2-3 days maximum. The next cycle, I was late by 4 days September 14, 2016, which ha snot happened to me for some time now. And I bled only for 1.5 days and that very scanty and not at all like my normal periods. I had taken HPT by then which were negative. Post two week of my September periods, Iwent to the doctover and she asked me to take a blood test. My HCG was less than 2 in that test. On October 7, 2016, I took another blood test which showed levels less than 1.2. So pregnancy was ruled out. I was put on Meprate to regulate my periods from Oct 2 to Oct 9. I got my period on Oct 15, but my periods is even more scanty this time. I am due to be engaged next month. And I am very scared that I am pregnant as I have been reading cases where women have had negative blood tests and yet have been pregnant. My october periods was extemely scanty like for just half a day and then a lil bit the next day. Please suggest if there is any chance of pregnancy at all.