hey, im alma and im 13 years old im in 8th grade well i had my period when i was 10 and i had it normal at the ages of 10 and eleven but even though i had it i still didnt come regularly then at 12 at that whole year it only came 1 time than it stopped after and then during the summer around july 2011 it stayed a whole week it was during the last week of july through 3 days of august which on the 19 i would turn 13 then it stayed for a week and 3 days it was a heavy bleeding period with alot of cramps and bloating with fatigue after till this day 1/13/2012 it never came sometimes if feel like it wants to come but when i go check there is no blood.what should do and what do you think might cause this