Hard time breastfeeding HELP!?!

My daughter is just over a month old. She is my only chid. I am doing the whole breastfeeding thing and it was going pretty well for awhile. I have run into problems. The First problem. The hospital gave me a nipple shield because she could not latch on after an hour of trying. BIG MISTAKE! They gave me this rubber monstrocity with  no instruction! They did not tell me to use it for a few mins then take it off. I am still having to use this thing. If I lost it i would be in a world of trouble. If you are pregnant PLEASE BEWARE! This nipple shield can cause more problems than just something else to keep up with, such as a lessened milk supply. It keeps the baby from stimulating your nipple fully, so you dont produce milk like you should. I worked to get my milk flow downpat  using a pump to empty my breasts comepletely after every feeding. thank gooodness that part is over.

Now onto the current problem,  My  baby is not getting full on my breastmilk. it does not matter if i sit down and feed her for hours or if i pump and feed her with a bottle she is satisfied for 10 to 20 mins then she acts like she is starving. I can feed her 4 or more ounces of breast milk and she is still hungry. i have tried supplementing with a few ounces of formula after the breast milk and she seems to be fine for a couple of hours. Is this something wrong with my diet? Is this wrong of me to do? Is there a better way to satisfy her? Please any one with a somewhat educated opinion on this help me, I just want the very best for my precious baby.