Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with a doctor.
Without the ability to examine and obtain a history, I can not tell you what the exact cause of the symptoms is. However I will try to provide you with some useful information.
Stress and depression can cause your body to outwardly express symptoms that are sometimes hard to explain and describe why. However, given your history, do your doctors believe your symptoms could be due to low vitamin B12? Vitamin B12 deficiency classically causes difficulty with sensation which can affect walking. It typically begins with mild general weakness and paresthesias mostly in the hands and feet. As the disease progresses, if left untreated, can cause gait abnormalities. Cognitive changes can occur ranging from apathy, irritability, somnolence, and emotional instability. Treatment is with B12 supplementation.
Additionally, hypothyroidism can cause cognitive slowing and also muscle weakness. Treatment is with supplementation.
I suggest you continue following up with your physicians. You may wish to have your B12 repeated along with other markers of B12 deficiency (such as MMA and homocysteine).
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.