Does dermatographism make you itch constantly? i have it & it was controlled by zyrtec (cetirizine) daily but that's not even helping. or can it be something else?

Well no, but...: dermatographism is a physical exam finding that refers to the eruption of a hive with pressure, so it can't actually cause anything. But it is an indicator of eczema or general skin sensitivity to pressure and often irritants. Zyrtec (cetirizine) is pretty good at suppressing hives, but finding then avoiding your trigger is the best way to deal with this condition. Avoid fragrances, dyes, scratchy clothing...

Usually not: Dermatographism refers to an oversensitive skin which welts up when scratched and itching is not usually present. However dry skin is a common cause for itching and may be associated with dermatographism. Try applying a moisture all over your body <3 minutes after bathing (avoid scented soap) regularly and see if this helps. If not, see allergist.