Period irregularities. It with diet!

I have been facing two period in a month at a gap of 15 -16 days and I am working women with hypothyroidism for 10 yrs on medication of 100 mg aged 39 yrs. I had faced this issue same time last year and found thickening endometrial lining which without D&C and 3 month medicine course of cycloreg plus dupaston had got cured but now again since December I am facing this issue ... in December I got my period on 2nd Dec and then again on 16th dec and both times period flow was normal then I got my period this month on 5th January and now again on 16thJan .. I got my heamoglonin checked last month and it was 12 .. pls advise as can this be common if I am approaching my perimenopause and yes I am overweight my current weight is approx 86 kgs and I am trying to reduce it with diet