Sudden weight for no reason and hard to loose I am dieting and exercising?

'wt. Gain' =thyroid. If you mean 'sudden weight gain' then I recommend getting seen by your primary physician to get thyroid check. You may be developing hypo-thyroidism or already have it. Some of the tests may include: TSH, T4, ft4, ft3 & thyroid antibodies (tpo, thyroglobulin).