I just want to second what Barb says about the wet nappies over the first few days. My DD # 2 didn't harldy have any wetness in her nappies (hard to tell too b/c of the hospital using disposables, so I put cotton balls in her nappies) but she still was doing well, so don't go off that solely.

My DD lost close to nearly over 10% of her birth weight & I started to feel some pressure from the midwives about top ups etc...but I put my foot down & engaged the hospitals lactation consultant and put in place a 'plan' with her. (three hourly feeds amongst other things) If I ever felt a little under pressure about comp feeding etc... I'd tell them that I was following the plan set out by the LC & they left me alone. On discharge from the hospital DD # 2 hadn't gained much weight back (20 gms from memory) but I told them I was following up with the LC (which I was) and they didn't say anything more.

If you can, engage a LC upfront for reassurance and support.