What Causes Darkening Of Neck Skin With Tiny Itchy Warts?

My neck is extremely dark and I have small warts growing on it, they itch a lot when I sleep at night or when I am exposed to the sun. Secondly I don t seem to empty my stomach. I drop one stool every 5 days and I can feel I need the toilet but nothing comes, as a result of this I now have a sharp burning pain on my left lower rib