Is Breast Feeding And Thyroidism Related To Loss Of Menses Postpartum?

I delivered a baby 6 months back,, i have been breastfeeding the baby but he is not completely on my milk alone from the start. But till now I have not got my periods. This is worrying me, is this normal? I have also been diagnosed with postpartum hyperthyroidism first which slowly progressed to hypothroidism, but I am not under any medication now as my doctor thinks that my thyroid levels may get back to normal. All that I am worried about now is that I have not got periods after delivery till now...