Grave's disease is the commonest cause of hyperthyroidism (excess thyroid hormones) and its effects on your body is akin to everything "speeding up". Your metabolism speeds up so you lose weight and feel hot and sweaty, your bowels move faster so you get loose stool/diarrhoea, your heart speeds up so you may notice that your heart is beating very quickly, your mind is very active and may have difficulty sleeping and you may notice some tremors in your hands.
These are some of the signs and symptoms of hyperthyroidism. Our main concern is the heart, because if you heart keeps beating too quickly for too long, you may develop heart failure. In severe cases, thyroid storm may develop. This is a life threatening condition where there may be manifestations such as heart failure and you may become drowsy/confused/have a change in mental state.
Treatment is essential and involves medications to block the thyroid gland from making more thyroid hormone. This group of medication is called Thionamides and Carbimazole is one of them. Another medication is given whilst the thyroid hormone is still high to bring down your heart rate. You will need to be evaulated by your doctor who will determine whether or not it is safe to start it.
I'm afraid alternative therapy and nutrition treatment cannot replace medical therapy for Grave's disease. Carbimazole should only be stopped at the advice of your doctor as he/she will be able to determine whether or not it's safe to stop. If you suddenly stopped taking Carbimazole and switched to alternative therapy, the diarrhoea and weakness that you're experiencing is possibly the result of high thyroid hormone levels.
I would suggest seeing your doctor as soon as possible for an evaluation. If you stopped Carbimazole because of some side effects that you're experiencing, please discuss this with your doctor as there are other medications available.