Many health care professionals will tell you that breastfeeding isn't supposed to hurt. Well, most of the moms I have talked to have had experiences ranging from minor discomforts to mastitis and severe cracked nipples and infection. Breastfeeding is best for baby and many of the discomforts will be gone within the first days and usually don't last longer than a month.
One of the most common complaints is sore, cracked nipples. It can make is quite painful to feed your baby so when packing your hospital bag, be sure to include lanolin or balm to help you heal faster if you start to have any soreness or cracking. Also, alternate between heat and cold especially when your milk is first coming in. A warm wet towel will help with the "let down" and cool towels or ice packs can help sore engorged breasts. For really quick relief, keep a couple of wet nursing pads in the freezer. When you need some relief, just place them in your bra. Remember that breastfeeding does get much easier and may only hurt in the first little while. It is so worth it to push through that challenging time for the benefits that breastfeeding will provide to the baby and to you (getting back that body, lower risk of some cancers etc). Hang in there and contact your local La Leche League for support and information. Here are some helpful links:
In Canada http://www.lllc.ca/
In USA http://www.lllusa.org/