The first thing you need to do is get your scalp checked out by a dermatologist. It is entirely possible that you are suffering from a problem such as psoriasis, and this cannot be treated in the ordinary way using medicines. It would have to be a long term treatment that would also involve adopting a lot of home remedies. Please do keep in mind that there is no solution for a skin disorder such as psoriasis and the only methods available to patients are homeopathic and herbal based. If possible, it would be better to find a doctor who would be practicing homeopathy, herbology, Ayurveda or naturopathy in order to help with this. If the dermatologist can come to the conclusion that you are not suffering from psoriasis, then get yourself checked out for dandruff which is eczema related. Those who have eczema can also suffer from really painful dandruff like the kind you have described. Once again a skin problem with no cause or no cure, eczema can only be controlled using creams and applications and taking care of the diet. Eczema is basically nothing more than excessively dry skin which can turn infectious if not taken care of quickly and effectively.
Usually, the best solutions for dry skin are oil based. But if there is dandruff in the picture, then oil cannot be an option, because the presence of oil will only worsen the dandruff situation. Instead, it is a better idea to try and take care of the dandruff first. In order to do this, you would need to maintain a clean scalp. Try to use a shampoo with conditioner, so that there is no requirement for oil. Once a week, apply fresh lime juice to the scalp. Since you are suffering from such large flakes of dandruff, try to dilute the lime juice. It is possible that there are raw patches on the scalp, which may end up burning severely if you apply concentrated lime juice to them. Leave this juice in for a while, as long as you can take it, and then wash off with plain water. It is a good idea to cut your hair short so that the problem becomes more manageable. Make a mixture of one part of light olive oil and one part of powdered camphor crystals and then rub this into the scalp. Wash after about 45 minutes. Please do not let this remain for long.