Treatment for Mottling Skin?

Whenever the temperature is cold I get mottling skin. My skin only looks normal when the temperature is above 85 degrees. I started to to get mottling skin about 3 years ago. It started as this red patch in my foot. Then it got to my legs. Now it's starting to go threw my arms. Why is it spreading? Is there anyway to stop this? I've seen a dermatologist and he said that it's no problem. I should only contact him when I feel pain. Right now I don't feel pain. I only feel colder than other people. Oh and this started when I got my period. Does this have anything to do with it? I'm not overweight. My BMI is normal. My parents say that exercise should help. Is that true? Please help!


Thank you