Ovulation Cramping and Flashing Smiley on OPK

We’re currently in my 4th month of ttc. I just started using the clear blue advance ovulation tests this month. I got a low fertility on my first day of testing followed by 6 days of flashing smiley faces. No solid smiley yet, but last night I had what I assumed was ovulation cramping complete with throbbing in my thighs. Yet still today I had another flashing smiley. Is it possible to ovulate and not have the test pick it up? Trying to figure out when I’ve ovulated or am ovulating because I need to have blood work done 7 days after ovulation at the doctor’s office. Any insight would be greatly appreciated.