I understand OP, if I saw those lines, however faint, I would be wondering too.
This month I was over a week late on my period, for the first time TTC in many years and the first time in years cycle went like this, and stark white negatives the whole time. Wondering what went on.
I read an old post on here I found very helpful explaining the science behind it - https://www.mumsnet.com/talk/conception/3218493-preggo-test-science-for-TTC-geeks
and also this site it has stats on test results days past ovulation etc - https://www.countdowntopregnancy.com/pregnancy-test/
From the science post, I learned that sperm can live for 5 days waiting for the egg, we can ovulate earlier/later than when we think (the only way to absolutely 100% confirm/pinpoint when ovulation has definitely occurred, is to be medically monitored with scans I think). We can also implant earlier or later (6 days to 12 days), and also in each woman 'baseline' (non pregnant) HCG levels can vary a lot, as can time to double.
The NHS website states urine tests are accurate 14-21 days after intercourse occurred, but obviously if you are having regular intercourse, this could be anytime.
So it's really variable between each woman and even each month. With these early tests being so sensitive, a lot of very very early pregnancies are being detected even if they don't progress. I understand how this feels, as I've had miscarriages at 5 weeks previously.
I hope this month turns out to be a success for you (how certain are you that you are 13 dpo? and have you DTD regularly? cause I only DTD once last month and I knew negative meant negative at 3 weeks post DTD), and if not then very soon. xx