It varied with all 3 of my pregnancies. I can't remember with DS1, but DS2 was quite early. I remember finding a positive before the 4 week mark. The GP wanted me to do a blood test just to confirm as I think it was only around 3 weeks from last menstrual cycle. Then with DD, it took ages to get a positive test. Much longer than for the boys' pregnancies. I used the same brand home test too, so not sure why it varied so much?