What Causes Reduction In Flow During Periods And Weight Gain?

i started gettin my periods at da age of 12. they were regular before.. tilda age of 15. but then it went irregular for 3 months or so. i concerned a gynac n she gave me dievery tablets.. i got my periods in 10 days. this happened twice..
now my periods are regular. but the flow has reduced to 2 days which was for 4 days previously. what can da reason be.? m i attainin meno pause ? m only 22 now.. also my waistline has increased to 30 from 26. in four years.