4 heavy periods in 6 months

I am exactly 6 month PP. I had twin girls via emergency C section at 33 weeks due to PPROM and Pre eclampsia.

Also my babies are IVF twins after a long history of infertility with severe endometriosis/adenomyosis/repeated IVF failure.

My pregnancy as such was smooth - zero symptoms and aches/pains until the end.

Girls are thriving, I am pumping close to 45oz per day and top up about 15oz formula.

I started my first period exactly 3 month PP. Heavier than normal, soak through a pad in a few hours, bleeding through things, lasted 4-5 days.

Then I started getting it every 21 days. Now at 6 months PP, I have gotten 4 periods. All heavy and lasting 4-5 days.

I am meeting PCP today to get labs done. I want to check for thyroid dysfunction and anemia and ferritin etc.

Any other suggestions? Anyone else can relate? Thank you.