I took a home pregnancy test on July 25, it was positive. Two weeks before it was negative, although I had symtoms of being pregnant. My cycles are irregular and I believe, not 100% sure, that the beginning of my cycle was June 16th. I also had intercourse with someone other than my significant other on July 9th. My doctor told me that I was 5- 5 1/2 weeks on August 1st because the baby's heartbeat was visible.. I want to believe in my doctor that conception did not happen on July 9th, but I have been feeling skeptical. I also had slight bleeding, which I believe to be implantation bleeding around July 19th. I hope someone can confirm my fears just pure guilt.