Has your doctor diagnosed post partum thyroiditis (PPT
Your TPOab is somewhat elevated, which usually indicates PPT. It's considered a variant of Hashimoto's thyroiditis, which is autoimmune thyroid disease and the most prevalent cause of hypo in the developed world.
PPT is usually a temporary condition characterized by an initial hyper phase, a brief return to normal and then a hypo phase. Hashi's, except in its very early stages, usually causes hypothyroidism.