You didn’t get pregnant till near the end of July if you were only 6 weeks on September 4
Funny thing is I conceived June 28-30 as well and took test July 14 and it was negative then I realize I missed my cycle July 24 so I took another test and it was positive . I’m 16 weeks today
That timeline seems wrong. If you ovulated some time near the end of June, and then in early September, you'd have been like 10 weeks. I'd say it's much more likely that you got pregnant in late July or early August.