I've had 8 days of flashing smiley OPK. What to do?

Melissa • TTC 3 years. IVF BFP 9/17. 🥚due 5/18
I'm not sure what to do. This is the first month I've used an OPK - I chose clear blue advanced. I had two days of low then it went to high. Should I worry? Should I keep testing? You only get 10 sticks per month and I'm not sure what to think