Ovulation question

Tracy • 26 Mommy to Taya ❤ 10-24-16. In love with my solider. Baby boy💙 6-15-19
So last month I started using the clear blue ovulation kit and got my solid smiley face on CD 16 and according to glow and my bbt chart I ovulated on cd 17. Well today on cd 16 I got an empty circle. If you have regular periods is it normal to ovulate on different daya