Testing for early pregnancy

I have PCOS. I tried PT 2 weeks after missed period (I used Periodic tracker, so even I have PCOS I know when to expect) -it was negative. after 4 weeks from my last PT, I still don't have period. Then symptoms are already showing (nausea, vomiting, heightened sense of smell) Though I'm hesitant to try another PT. I did it anyway- POSITIVE! It means, 2 weeks is till early. The positive PT reflected on my 6th week or maybe less than 6th week but more than 2 weeks. only if i did PT earlier.