There can be a number of reasons why you are feeling cold. One of the most reasons common in women particularly is an under active thyroid gland. The thyroid hormone helps in controlling your metabolic rate, and the quicker your metabolic rate, the greater the heat production. This means if you have to little thyroid hormone, it slows down your metabolic rate and less body heat is produced. Another cause of feeling cold is basically being thinner than usual, which means you have fewer insulation around your body to help in conserving your body heat.