Hypothyroidism is a common cause of heavy menstrual bleed along with weight gain .
However, if u have supplemented the thyroxin correctly, the symptoms should go away
If still not, it's better to get yourself evaluated thoroughly.
Also weakness can be due to anemia because of blood loss. U have to supplement iron n vitamins as well in ur diet and medications.
Next Steps
maintain menstrual diary.
get ultrasound pelvis done,
complete blood count, recent
TSH values.
Health Tips
it's always better to consult a Gynaecologist if due to heavy menstrual bleed ,you are having weakness. it simply suggests that active intervention is needed.