What Causes Skin On The Arm To Hurt?

My skin hurts on the back of my arm. Like a bee sting. Hurts especially when touched. It looks completely normal. This is the third day of the pain. I also am getting this feeling of bites all over my body. Both sides, legs and butt mostly. Sharp like twinges. Age 32 Height 5' 8" Weight 138 I am not on any meds. It has been two weeks since I took a multi vitamin. (it was changing my hormones, i think, and too much caffiene in it)
I eat healthy all natural foods and have no allergies. I have 3 preschoolers. I am a stay at home mom.