What Causes Rashes All Over The Body?

i have a rash all over my body? other issues are joint pains mostly hips knees? Muscles stiffness, feels like my glands are swollen, cant sleep they start as little bumps not visibly discolored then become pink little pin top bumps then eventually the size of a small pimple. no puss no other thing! Went to ER because i got sick as well they said contact dermatitis but been on meds for 2 weeks no progress! I have been tested for lyme awhile back due to tick bites that led to me getting very sick and an infection in my abdomen that was the size of a football! I also get zaps in my head! like old tvs when the picture is going out!