Hi, Severe tiredness, constipation, weight gain, forgetfulness , dark circles under eyes and all these symptoms can be due to Hypothyroidism and normal TSH does not exclude unless there is low Free T3 and Free T4. I would advise you the following in such a situation: Repeat Thyroid function fully. Consult your Psychiatrist as you have adult ADD and get treated properly as such problems add to the symptoms that you have. Consult a Dietitian so that you have have diet adjustments to reduce weight. Start exercises as this gives all positive things like better oxygenation, reduce weight, feels good and raises self esteem. Thus helps to overcome the problems. Also consult a Obesity specialist so that a complete clinical evaluation, examination, relevant supportive investigations can help to get the cause and get treated accordingly. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. T Chandrakant, General Surgeon.