What Could Dry Patches/spots Between Chest Suggest?

I am 20 years old. Since i was about 12 i have been getting little dry patches of skin between my chest, it sometimes spreads to my stomach or onto my upper chest. It has also shown up on the sides of my breasts and on my arms between my armpits and elbow. Also have had a few at the bend of my elbows before. They do NOT itch. Moisturizing does seem to help. In the shower when its really bothering me i scrub or sometimes scratch it off. Easier when wet. It does go away, but always comes back. A few times a year. Ive also noticed white spots on my stomach lately. Maybe just sun spots from tanning. But one are under my breasts where i usually have these brown dry patches i now have white spots. What could it be!?