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).