Ouch...that sucks...fortunately I had it when I was very young, and I don't remember a thing about it...
Calamine is a joke....I just like to think of it as being a mixture of water and flour -- It does nothing for me except help to dry out blisters from poison ivy, but it's really not even very effective at doing that.
Anyway, what I found to be the greatest thing to stop itch from when I get poison ivy is to run hot water over it. For example, if I had it on my arm....I'd put my arm under the faucet....I'd first start out with warm water, and increasingly let it get hotter and hotter until I couldn't take any hotter water...let it run for a few seconds, and then I'd pull my arm out...it'd take away the itch for about 10 hours.
So, my recomendation...extremely hot baths.