First time using opk’s

Caitlin • 1st born May 2017, 2nd born May 2020, 3rd due May 2024 💗

Okay so TTC baby number 2. Got my iud out in May. This is my first month using opk’s. Cycle length is between 26 and 29 days since I got the iud out. I’m on cycle day 15 and I haven’t had a positive opk yet. In fact, the line isn’t getting darker at all. I expected to have a positive opk already since my last cycle was 26 days. Is there a chance it’s still coming? Or am I not ovulating possibly?