Hi, welcome to the ehealth forum and I am glad to help you.
Based on your description it seems that your concern is with functioning of thyroid gland at elevated levels, that is, hyperthyroidism. The main symptoms of hyperthyroidism include weight loss, anxiety, intolerance to heat, hair loss, muscle aches, weakness, fatigue, hyperactivity, irritability, apathy, depression, polyuria, polydipsia, delirium, tremor, pretibial myxedema, and sweating. Additional symptoms such as palpitations and arrhythmias, shortness of breath, loss of libido, nausea, vomiting, and diarrhea can also occur. The diagnosis of hyperthyroidism is confirmed by blood tests that show a decreased thyroid stimulating hormone (TSH) level and elevated T4 and T3 levels. There is possibility of coexisting IBS as per your complaints and normal investigation reports. You must consult your doctor for definitive diagnosis and therapy as the same cannot be ascertained online.
Hope this helps. Take care.
Note: This post is not to emphasise final diagnosis as the same cannot be made online and is aimed just to provide medical information and no treatment suggested above be taken without face to face consultation with health care professional.