Mate, some GPs are friggen hopeless, just because they are docs doesn't mean they know everything about health and medicine, I mean, they might of only just scraped through on their marks for their degree, how would you know?. I use to bull shit my way out of work as a young bloke working for TNT, we had our own doc on the team and once I convinced him I had conjunctivitis, bahahahaa, couldn't believe he fell for it.
My family doc we use now however is really good, so my advice is to go see another doc, at the end of the day whats a couple of bucks when it comes to your health, not all docs are good, but most aren't bad either, so see another one and ask for a referral to a specialist if your not happy with the diagnosis. They are only human, they get tired and couldn't be bothered as well, so when you come in and aren't in absolute agony, he prob couldn't of gave a rats arse about you, go see another doc mate and get to the bottom of it.