A GP was also at a loss when asked, but within about 30 seconds my ob gave me a list of a dozen safe options off some database he had access to. Maybe GPs need to be reskilled at using drug databases? I don't really expect them to know everything, but I do expect them to take a patient's requests seriously and to be able to find the answer when they need to.
The odd good experience, I've had with a couple of GP's is when they've rung a specialist or a specialist within a hospital to get the answer. Sorry not to do with lactation though. Unfortunately it is time consuming for them to do that.