The normal range for Serum Ferritin for Women is 10-150 ng/ml. Your level is still in the normal range. Serum Ferritin reflects total-body iron stores, not protein. Suggest having your doctor do an "Iron Profile" blood work to see if you have something going on with your iron stores or not. Serum Ferritin does not tell the whole story.
Try taking an oral iron supplement. I know mine got extremely low and I had to take iron supplements and when that didn't work they had to give me an iron infusion.. Even try a multivitamin if you don't want to take just iron supplements.