I first started my period at age 12(but will be 13 that year).my first period lasted for more than a month!!then the rest wasn't that long any more but was always more than 7 days sometimes 2-3 weeks.but i feel fine no pain.however starting from last year my period lasted shorter around 7 -8 days but then I missed 3 months of period then after it came for like 7 days I think but since oct till now I'm missing my period?btw I'm now 16..what could be the problem??