Positive opk??

Julie
Does anyone know what could make your opk's
Light, dark, light and then dark again? Is that normal? Also, my temp did dip a bit on Friday and sat.. But the opk on Friday was light. The bigger opk.. The one on the right was from this morning. This is  so frustrating.. I have no idea if I have o'd or not. I had a chemical last month.. And so I have no idea. I haven't had ewcm yet.. And I usually do when I o. Has this happened to anyone?