i went through that too. using one was like a miracle to me in the hospital, as dd wouldn't latch.. and then, the pedi told me how it would eventually lead to decrease in milk supply and end bf early! it made me freak out.
i think i found a few good articles online, maybe even suggested by some people here. from my memory, though, what we did was this:
i changed the hold to cross cradle. for some reason that was better for us.
i used some expressed milk and a dropper.
i'd put some milk in the shield and put it on, let dd nurse for a little while, long enough to pull the nipple out. then i'd unlatch, put more milk on my boob, and try to get her back on. i had moderate success at first, but kept trying.
it really seemed like the end of the world at the time, as dd was quite the screamer (and wouldn't nurse when she was mad mad mad). letting her get a little milk in her to make her not freaking-out-hungry helped a lot. pulling the nip out helped a lot.here's
the kellymom article, and here's
an old mdc thread...
good luck to you, mama. it really will get better, i promise.