So I’ve been using ovulation tests since cycle day 10 consistently the same time every day. But have only had negative results

On day 16 I was having cramps which i thought was due to my period issues, and I also woke up with 3 huge spots on my chin.

I went for a scan yesterday on cycle day 20 as I was having a pelvic scan due to period issues.

But the nurse told me that she is pretty confident I have already ovulated possibly 3-4 days prior which would add up

Is it normal to have negative ovulation tests but still ovulate

I used clear blue