Afraid to go on the potty?

sunnyday016

DD has been telling us when she needs to go poop, but when I put her on the potty she immediately asks to get down, and then ends up going in her diaper a few minutes later. I was reading her a book while she sat there, but then I read in the 3 Day Potty training that reading in the bathroom isn't a good idea. We're not doing the 3 Day yet, but just trying to get her used to the potty. As of now, she's sat on the potty a million times but we've never had a "catch" for pee or poop.

 Any ideas on how to get her to actually go on the potty once she's there?