What Causes Itching All Over The Body?

I am always Severely itchy all over my body. This has been occurring since i was in grade school i am in college now. Specifically my thighs, legs, and back area. Just about everything irritates my skin. I try my best not to scratch the areas, but sometimes its so bad I can t resist. When I have my scratching episodes sometimes ill get bumpy inflamed spots on my body which kinda resemble bug bites, that although i am itchy all over my body it only accumulates in the specific areas I had mentioned above. Do you know what may be causing this or what i can do to stop it?