Congratulations! You know, it's VERY hard in the first few weeks with a new baby. Everything you see in movies and tv is all "smiles and joy". Don't get me wrong, having a newborn is a joyous miracle. However, trying to adjust as a new mommy on little or no sleep is tough. We've all been there, and it WILL get easier!!! My two children both lost a little weight right after they were born, but they gained it back by their check-up day. I also exclusively breastfed. It's very hard in the beginning, but there is a lot of support out there. You can call your pediatricians or OB's office (or even the hospital) and ask for the number of the local le leche league. Their job is to help new moms learn how to breastfeed. Although I found the le leche league lady to be a bit annoying when she visited me in the hospital, she did give me great advice. Sometimes just changing the way you hold your baby, or the way you sit or lay will greatly help.
I never used a breast shield, so I am not familiar with them. I did pump with both of my children, though. I used a Medela electric pump, and I loved it. I still remember sitting in the dining room, trying to pump the day I came home with my first son. I was recovering from a c-section too. My brother and sis-in-law were here to help. I remember having an emotional breakdown in front of my bro-in-law as I sat there pumping. I laugh about it now, but it was bad at the time.
Yes, I remember my breasts feeling empty after pumping. They will fill up soon enough, and your body will eventually adjust to making the correct amount of milk. I think that's so amazing.
I know the lack of sleep, baby screaming phase is not pleasant. It will get better. The one thing I found that worked was using those velcro swaddling blanket wraps. They stay on better than a regular swaddle-wrapped blanket.
Hang in there!
-Jen