Clearblue easy digital OPK

So I find myself questioning how accurate these things are. Last month it told me I was at peak fertility for like 4 days in a row. This month, on cycle day 7, it told me I was at peak fertility. I have never gotten a flashing smiley to say I'm at high fertility. It always just goes straight to the bold smiley for peak. Anyone else have any stories/ success with these? They're not the cheapest, so I can't decide if I want to continue using them in the coming months. I mean are there such things as false positives? I know you can get a positive and not end up ovulating, but can it just be flat out wrong? Sorry this was a little long! Thanks for reading and any comments!