Why do so many girls ( and women) think they are pregnant if thier cycle deviates the slightest bit?

Lol!!! It really makes you wonder what are they teaching them? Or maybe they use this forum for a substitute for a regular doctor. I personally know of a young lady who got pregnant , and kept thinking that it had to be something else besides a pregnancy. She kept insisting that there was no way she was preggers as her BF had pulled out. Should have seen the look on her face when the dr. told her differently.I read alot of these for the entertainment value. :)