Clearblue fertility monitor not accurate ?

So I just bought the clearblue fertility monitor after 6 months ttc after loss. This is my first cycle trying this and on day 6 (the first day testing) it immediately said I had an estrogen surge even though I don’t ovulate until around cd20 according to opk’s & bbt. So now I’m on day 15 & fertility still reads high but all my cheapie opks are still low. Has anyone else had this issue? Are these tests not really accurate?