The whole part of my body is itchy what treatment should i buy to stop it?

Diffuse Itching: Diffuse itching can be treated by taking antihistamines such as Benadryl (diphenhydramine) over the counter, taking cool baths, etc. However the larger question is why is it happening? I notice that you are on Lamictal, which can cause a very severe whole-body rash called Stevens-Johnson syndrome. I would contact your doctor in the morning to discuss this and go to Emergency if the skin condition worsens.