Can 5lb weight gain post partum(1 year) cause periods to stop?


So I had my baby on january 20th 2017 and till november I was having regular periods. But since then I dont get any periods neither am I ovulating(opk tracking). So I told my doctor about this when I skipped my first cycle she said that I should take progesterone to kick start them! So I got my period straight on january after the progesterone course.

This month I am again period-less ovulation-less symptom-less and clueless.

So I called my ob/gyn and she asked me to take the pills again.. BUT Thats the problem... I am ready to take the pills but I want to know why????

What happened to me suddenly??

So she said... oh that because you gained 5lb after having your baby. Pre-pregnancy you were 113lb..what????

So let me tell you all something about my weight history! Then you guys tell me if she is right or not...

I was 85lbs(underweight in my college-june 2015)

After getting married I gained 10kgs and became 109lbs-2015 november

And within 6 months of marriage i got preggo with a weight of 113lb to start with i.e., May 2016

But my Aunt flo was never late, like she was the most punctual clock-work thing in my life, visiting me every month with her ugly face! Even after my son was born she came regularly 10 freaking months (forget about post partum irregularity)

So I do not believe I can be so sensitive to a 5lb gain which is the same since ds was born-118lbs...

I just know something isnt right in me. I just know there is some reason for it and not just stupid 5lb gain.

But how do I convince my doctor or how do i know? I am just so confused!!