Ferritin level continues to decrease

I have been anemic since I was 11 years old but after a C-section 3 years ago and a referral by my gynocologist, I have been visiting a hematologist for the past 3 years. After 2 years of Iron infusions, my stored ferritin levels would raise for a short period of time and then decrease. I have been examined with endoscopy, colonoscopy, bone marrow testing, stool cards, and thyroid blood test and they all come back normal. I do not have heavy menstrual cycles. I am feeling less tired due to a prescription of ICAR-C Plus (Iron, Vit C, Cit B12/FA) but my Ferritin level has dropped form 210 to 65 within 4 months. Now my doctor wants another stool card. I am trying to find out information to help me with my next visit so that the research on my condition can progress instead of what feels like going around in circles and repeating tests that have already proven normal.
After reading through other posts, I wonder what the next step is?