I would suggest a body wash without any soap. That's what I use and it seems to help a bit.. As to what is itching, I don't know. I have the same prob. Always scratching but nothing really there to scratch. I think mine is old stretchmarks coming back to haunt me with this preg as well :-\ lol
I hope things get better. Maybe calamine (sp?) lotion might help when at home, but its not the prettiest of stuff to wear out, lol.
Good luck