Welcome to HCM,
After going through your history,you are having Hypothyroidism
and taking Eltroxine you have not mentioned what strength you are taking and what are your values of T3,T4 and TSH.
I presume you must be taking your Thyroxine
supplements regularly with periodic check ups.
Your breathlessness may or may not be related to hypothyroidism, hence you should visit Endocrinologist/Internal medicine specialist to examine and investigate for any cardiac or Lung pathology may be Complete blood count
, an X ray chest, ECG and Pulmonary function Test. Thyroid function test and if required Echocardiography
Treatment depends on cause and for Thyroid please take your dose Eltroxine regularly and if required your doctor will increase the dose to your requirement.
Sudden loss of family members do cause emotional trauma, with time you can bear this.
Please take care of your health.