Welcome to HCM,
You are hypothyroid for last 15 years,I am sure Levoxyl in right dose to have optimum control of Hypothyroid state.
Your symptoms may not be related to low thyroid hence you need to be evaluated by Physician and Psychiatrist
to look for signs of depression.
If there is no other organic cause then proper anti anxiety and anti depressant
treatment with proper psychotherapy
will work for you.
Please do not lose heart.
You can also try exercise daily and some kind of yoga and meditation
will be beneficial for you.
Please take care