One OPK was negative and clearblue was positive!

Ok what does this mean? My first urine this morning using a Proven LH strip was negative. The clearblue digital showed a flashing smiley face,....so high fertility. I did the LH strip again at 1pm..still negative. And not even NEAR a line on the LH strips that would even look like high fertility was approaching. It was a very faint faint line next to the control one. So which test is right and how can I have two very different responses? I should add usually my CM when I ovulate is EWCM and this time it is watery.