Famale Question

I had an IUD placed 2 yrs ago 6 wks after giving birth.......I had NO period up until the month after getting my band and it's been coming every 3-4 wks!!  I thought my IUD had become dislodged or something. I went to my GYN, they checked all kind of tests, smears and even did a MRI.....and could find nothing.  It's all do to breaking down fat cells and releasing estrogen.....My cycles are becoming lighter and less frequent..........as though the wt loss has slowed down considerably!!