What Causes Reddish Brown Patches On Chest Which Is Spreading?

I have redish brown patches on my chest that seem to be connecting and spreading very slowly...most if the time they are brown..but once in awhile they turn a slight red,,,they do not itch or have any lesions...I also have a little on the bottom of my neck...the blotches arnt dry ever either...just want to know cause its kinda scaring me!!