Well you are suffering from this condition known as Multi nodular goiter. Goiter refers to the enlargement of the Thyroid gland. Here, the Thyroid nodules appear lumpy with multiple nodules. This occurs mainly due to fluctuation in TSH levels. Other causes include iodine deficiency, goitrogens, hereditary.
Since your mum and grandma also had goiter, it is mainly hereditary. Your scan reports suggests that you have multi nodular goiter, which has caused compression of the trachea. I would suggest you to get an FNAC of the thyroid swelling and along with the TSH and T4 reports consult your doctor for further treatment.