Thank you for the information,
As per the symptoms you are experiencing , it seems that you are suffering from hypothyroidism after the thyroid surgery.These are common symptoms after complete thyroidectomy.The symptoms are weight gain, lethargy, depression, decreased libido, hair loss, low heart rate etc.
You should have the repeat thyroid profile done now to know the present status of the thyroid hormones including tsh, ft3, ft4, parathyroid, serum calcium, etc. after consulting your doctor.
The endocrinologist will be able to help you better regarding your symptoms.
The thyroxine tablets are usually prescribed after the surgery to replace the hormones.
Let me know if you have any doubt.