I had a CVS done at 12 1/2 weeks (wouldn't do any sooner, I'm in Australia) and apart from the pain (yes it did hurt) it was fine.  I really think it's a personal thing about whether you want amnio or CVS with pluses and minuses for both.  You shouldn't though have to keep taking the dex if it's an unaffected girl so I'm not sure why the doctor said that, I'd get a second opinion or do some research on the internet. All the best for you and your babe.

LIsa D