Been on remeron (mirtazapine) 45mg at night for three years and i've gained yo much weight and here lately no energy depressed can't even get outta bed ?

Treatment Failure: When a treatment fails or has too many intolerable side effects the prescribing physician needs to be contacted so that a new plan can be developed.

It is best to discuss medication with your Psychiatrist who knows your medical history for a thorough evaluation and recommendations for treatment. If you are not confident with your Doctor please see another for a 2nd opinion. Have a physical exam to rule out illness and see a Clinical Psychologist with expertise in multiple forms of psychotherapy .