Ovulation days ?!

Ciaraleaf
I cannot seem to work out when my ovulation days are? I've used Walgreen own brand strips but they don't seem to be accurate. The app says it should be around my 15th day my Chinese GP says it should be around my 8th day?
Any advice in how to work 
it out? 

Glow Resources

Let’s Glow

Glow is here for you on your path to pregnancy

Glow helps you navigate your fertility journey with smart tools, personalized insights, and guidance from medical experts who understand what matters most.

25+ million

Users

4.8 stars

200k+ app ratings

20+

Medical advisors