Multiple days of low “O” result on Clearblue adavanced?

Dana

I have tested for 4 days now with the clearblue advanced opk and have gotten 4 low or empty circle results. Has this happened to anyone before? This is my 5th or 6th month using them and I always only get 1 empty circle (the first day I test) and then flashing smileys until I get peak. Is the test stick bad? Or is this normal?

Thanks!