Because I don't really know how my own body works - I can't tell the difference between cervical mucus at different times of the month. I find the whole concept a bit frightening tbh 
I don't have symptoms when AF is due and have maybe 5 periods a year at random times though maybe that's improving as for the last 3 months I've had a period at similar times in each month, but before that I didn't have a period for 7 months (wasn't pregnant either) it's really weird. I just feel so alone because my body doesn't work as it should and it feels like everybody else knows their body so much more than I know mine!
back home in the UK nobody took me seriously because I hadn't gotten pregnant to have a miscarriage and was still having periods. Everyone always says if you don't conceive within x amount of time go to the doctor but we've been casually trying (sex every 3-4 days and no contraceptives)
For almost five years. I'm now finally getting serious about it, taking folic acid and eating better, no drinking and will be using ovulation kits so I have a better idea of what's going on. At least if it doesn't work I will go to the doctors again (where I live now though, Australia) I dunno why im posting really just feel like I should. Thanks for reading. X