La Leche League. If your OB or pediatric providers do not have a lactation consultant that they recommend, your next best step is to check out local and online resources through la leche league. They have state chapters and lists of certified lactation supporters, as well as online discussions mom-to-mom. You can get started at http://www.Llli.Org/webus.Html.
Ask your doctor. Nursing is one of the most important things you can do for your infant, but often it's much harder than anticipated. Unfortunately, the first few weeks are often the hardest and many new mothers get frustrated during this time. Asking your physician (ob and pediatrician) for advice and for recommendations on a lactation consultant might be all you need to get back on track.