Confused about DPO! Please HELP!!

Liah
Hi ladies! I'm new to this forum but have been using Glow since June. I'm 26 years old and my cycle is usually between 31-38 days. I'm currently on CD 36. (I haven't tested yet bc I'm scared of the possible disappointment plus I have no symptoms). My DH and I have been TTC baby #1 for 8 months with no luck. I've been using the clear blue digital OPK but I'm not sure it's accurate. I got a solid face on the 18th (with a flashing smiley face the two days before) which means I should have ovulated on the 19th right?? If so, I'm currently 18 DPO. However, I've gone as long as 23 DPO until AF comes. Is that normal??