I'm Pooped!

We've have got a battle raging against number 2 at our house. Lillie is great, even awesome about going number 1 on the big toilet BUT I can probably count all the times that she's gone number 2 in the potty on two hands in the almost 2 months since we've been potty training. Pretty much all the rest have been in her panties. We've tried bribery and taking away privileges but nothing works. I am so sick of cleaning out poopy panties, it's a huge mess. I know constipation can make kids scared of going number 2, but that's definitely not her problem. I know some kids want a diaper or pull up to go number 2 in, but she doesn't care. She usually won't even come find me when it's happened, I'll just find her...later. So there may or may not be poo tracked into the carpet. I need help! I'd hate to call it quits and put diapers back on, since she does so well with number 1. Any advice on things that worked for your kids???