6 days late, neg hcg blood test, never late,

Past: Two successful pregnancies and two ectopic prior.

First off, two weeks ago, I had an ultrasound to see if I was ovulating. The tech said my lining looked great and hinted there was something like conception happening. Period was due 8/25. 8/28 had qualitative hcg test and came back negative for pregnancy. 8/30 took urine test and negative.

I’m never late and now I’m six days late. If the qualitative test came out negative and I ovulated late... could they have given a false negative? If i ovulate late, would my hcg levels need more time to kick in? What level deems a negative reading for a qualitative test?

I’m more worried of another ectopic if my hormones are so low.