I'm 15, and I got my first period when I was 12. I can't remember a time when my periods were consistent and  I knew exactly when they were coming. It's always been a "Oh, look there's a cramp, probably starting my period today!" Kinda ordeal every month. The last two months though (August and September) have been kind of close. My period started on the 23rd of Aug. and on the 26th of Sep. that's the closetest they've been, as I recall. It's now the 13th of Oct. and I'm starting to have cramps, the semi-brown discharge and the cravings! Why can't my body just get on a normal schedule?! I want to be able to know when my period is coming, not a guess and check game... any ideas on what could be causing this??