I've been getting no lh surge on the clearblue digital ovulation test

Tamara • Mommy to my 2 beautiful baby boys, Nathan Louis💙 born August 12, 2017 and Parker Joseph May 6, 2019❤️ My whole world😍
I'm on CD 15. And cycle days are  usually 30-34 days long. My wedding month was longer. But I never know when I ovulate. I have been only testing once a day. When should I start testing twice? Have been testing ever since my period ended which was on the 8th. Always been doing FMU.