Itchy skin and odd bruise or hickey like rash after scratching.

I've always had skin issues. Most common as a child I had heat rash and allergy problems. But the last few years I have developed an uncontrolable itch. It affects my arms, legs, back, chest and stomach and no matter how much I scratch, what lotion I use, the amount, goldbond, lanicane, benadryl, hydrocortizone cream. I get no releif. So I scratch more. In some places I get a single small bump, skin colored that even the slightest scratching will cause it to bleed for no reason. In other places ( typically placed where I have stretch marks) the skin becomes red and inflamed and soon after turns into something that I can really only describe as a giant hickey, turning the stretch marks red and the surrounding skin purple and red with little red and purple dots around that. Its almost bruise like but closer under the skin like a blood blister or broken blood vessles. Can any one maybe shead some light on my situation? Or atleast tell me im not alone or crazy...