How To Solve Issue Of Not Getting Periods For Long Time?

i'm 20 years old, and the last time i got my period was last july 09. it's been 16 months since and until no, there're no signs or anything whatsoever (cramps..). i'm a little overweight(have always been) and i've noticed that i'm begining to bloat up a little.. the last time this happened was when i was 14 years old. i never got my period for 2 whole years... i'd like to know what can be done to solve it. i am definately not pregnant..