Re: 4 wk old won't BF, only takes bottle -- Help...
Welcome to the forum!
This link goes over techniques for getting a baby back to the breast: http://kellymom.com/bf/concerns/child/back-to-breast/. The skin-to-skin and instant reward techniques are said to be especially useful.
If your baby will latch on using the shield, USE IT. Every time she latches, that's a step in the right direction, even if the latch is a brief one.
Are you continuing to pump? Maintaining supply by pumping will increase the chances that your baby will nurse again, since her efforts at the breast will be rewarded. If you're having trouble pumping, let us know and we'll help you troubleshoot.
Please don't feel guilty. Nursing can be very challenging, particularly when your situation is complicated by something like flat nipples, mastitis, and/or a less-than-optimal latch.
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"