When we were having such a hard timing gaining weight as a newborn my ped's first plan was to give me the number for the LC's and tell me to call them as soon as I got home. They were never phased when I BF in the waiting room or waiting in the exam room or after vaccinations. I know they do have formula cans which they give to moms who are FF at but they do not offer it unless the answer to "and you are still nursing right?" is no.
When I mentioned we were co-sleeping the first time I expected to be given a hard time (ped is FAAP after all) but she was really supportive. She is always so happy and pleased when the sleep question gets an answer of 8 hours with a couple of wake-ups. I our ped. She is so reassuring about weight gain (or lack thereof) and all the other worries I have had.