What Causes Red, Itchy Bumps On Chest?

i have bumps, purpleness, and redness to the skin, itchiness, it burns, red splotches, on the neck, and chest, and inbetween breasts, any clue on what it could be? i am 15, 5'1, and 147 pounds, i have a history of spastic colitis, my tonsils and abnoids have been removed, and acid reflux disease, and also have been sick, puking since 2006 nonstop with no idea what it is. help me.