I have the Clearblue fertility monitor and for the past two cycles I have not shown high or peak fertility (even though I have the last four cycles). When I looked closely at the black sensor I noticed that it looks crooked. The lines used to be straight up and down, but now they are at an angle? Have I been inserting the test stick in wrong? Could that have shifted the black sensor? I've never gotten an error message, it just tells me I have low fertility. Do I need a new monitor?