Hook Effect??

To preface I have pcos, have had 9 pregnancies. I have 3 children. I Just gave burth March 2012, i have no had a period yet and have only had sex 2x since because i tore and stitches kelloid. July 28 I took a test because I was ceying for no reason. It looked neg. Next moring it was super positive. I quickly took another 3, different brands because i was shocked since we used protection those 2x we had had sex. For 3 days they were positive. Then they started getting lighter and lighter. Until i had what could be vvfls then i started spotting Aug 4th. I thought it was a miscarriage and thought that was that. The "spotting"/ pink discharge was there 4 days. Maybe 2x out of the day i had pink discharge. I made an appointment and he did bloodwork. Beta was <1. I thought it was very odd that it came back completely negative. I brushed that off. As the days passed ive felt more and more pregnant. Nausea headaches, thirsty, my uterus hurts in a bloated pregnancy type of way. I thought maybe i have another cyst. Then friday aug 19 i spotted brown again. Ive been taking pregnancy tests because i feel pregnant. Today Aug 21 i took a pregnancy test with mid day super diluted urine and got a dark positive again. We have not had sex so it has to be either the same pregnancy or something else. I have an ultrasound scheduled for sept 1st. We has sex Jun 16th and July 22. So id be either 7 weeks or 13 weeks by then. Has this happened to anyone? Was it a cyst, or pregnancy, twins or cancer? Im looking my mind. Any and all thoughts welcomed.