Negative tests but have symptoms

My periods are usually very heavy with alot of clots lasts 5-7 dsys, had period Aug 11-14 with usual heaviness, Aug 22 sex with bf,Aug 25 ovulation date, sept 6 had some 3 day very light spotting last day was brownish with no clots, period was due sept 8. Now i have most of the symptoms mildly, took 6 tests 5 of them were neg but 6th one was very very faint,wtf. Should be around 5-7 wks. With my daughter i took 13, 12 came out neg last one was very very faint,blood test had a low hcg levels & had to be comfirmed by a ultrasound was 3 months along.