Like she said, It is very common to have irregular periods after you have had a mc. I have had 2.. and mine were irregular for about 4 or so months after.
I have very regular periods I've never been on BC and I got pregnant in Feb 07 I ended up having a missed mc which was found at my 12w scan. I then went in for a DNC. I didn't have a period for 45 days after the DNC. I then had cycles anywhere from 30-36 days after always being 28 day cycles. I am now back to my 28 day cycles a year and a half later. Finally not having pregnancy symptoms as PMS symptoms last month. I'm trying to conceive again and it's a lot harder this time around.
It is very common for your cycles to be irregular after a MC. Weight can affect your cycle but usually not a sudden change after 8 years of being around the same weight.
If you don't trust your Dr I would suggest getting a second opinion.
this is from familydoctor.org
What about weight?
If you're overweight, your risk during pregnancy is higher for things such as high blood pressure and diabetes. You may also be less comfortable during pregnancy, and your labor may be longer. If necessary, use the time before getting pregnant to lose extra weight.
It doesn't say anything about miscarriage. i was 128 lbs when i had my miscarriage. it just means there was something wrong with the baby.
take care