Red small spots appear and disappear on my left leg. it's the same leg that always starts cramping up and falling asleep.

HIves?: The rash sounds typical for hives (transient or migratory red/slightly raised often itchy). When hives are associated with underlying muscle pain or neurological symptoms such as numbness/tingling, then one must think of immune complex disease, which affects blood vessels and can sometimes be localized. This should be examined by your doctor, dermatol, or allergist. Bringing photos will help.