Early positive clear blue digital opk

Yesterday I tested and got the low fertility symbol which is what I expected. Today I expected to get the same thing since I'm on cd13 and usually don't get my peak until around cd19-20 and it read that I was peak (solid smiley).  I took a frer to double check the results and got a line but not as dark as the control line. Does anyone know what might be going on?!