I breast fed all 3 of my children. Most of my friends breast fed. I don't know where the idea that a breast fed baby taking 10 days to poop is normal. The first 2 weeks after my eldest was born I went through 214 diapers. At her 2 week check up the doctor asked me if she was dirtying at least 6 diapers a day. I told him we went through 214 diapers and he had a cow. I thought something was seriously wrong with my daughter. But then we got down to figuring it out, and I explained that she would poop 3 times every time WHILE I was feeding her. No joke, I would change her diaper 3-4 times while she was eating. He told me to not stop feeding her to change her diaper anymore. My husband was pleased that we found a way to save on diapers.
The point being is that my kids and my friends kids were pooping several times a day (every time they ate).
Breast Fed babies do tend to gain slower, but they should NOT lose weight. That is a sign that either something is not right with the baby or the milk.
Just my opinion, get that baby to another doctor, and not in a month. Is this your first child? Sometimes you have to fuss a little more with your first because the doctors think first time mom's overeact. (Or change too many diapers).
Good Luck!
Terry