Should I be worried?

It's wierd, but recently I've had this compulsion to avoid sidewalks cracks. Actually, I used to do this off and on just to pass the time as I was going from class to class, but within the last month, I've been doing it more and it's not just cracks anymore. It's shadows, imaginary lines created by objects or where others were cut off. When I'm not thinking about it, I'm Ok but even when the thought crosses my mind, I can't dispel it and I can't compel myself to do otherwise. It doesn't make life difficult. Actually, it's kind of amusing but more often now I can't stop. I don't know why it's so hard to do something as simple as step on a crack. Am I alone and is there a reason why people do this? Tweet