Methadone side effects include light headedness, dizziness, extreme tiredness,so Methadone is the first to be considered as the cause of your symptoms.Ativan can also cause dizziness.
Have you checked your blood lithium levels recently? High levels of lithium in the blood can also cause dizziness and severe weakness.
Your doses most likely needs some modification, you should discuss that with your doctor.
You're much welcome and thank you very much for a nice compliments!
Take care of yourself for your 5 year old daughter!