leg problem with my baby?

so my son near beared weight on his feet since the day he was born! He has no interest in doing so either! his legs work fine (his left leg isn't great but he can still use it). where I live all children get free medical care till 6. but it also means you get put on a long waiting list to have your child seen (I was told I would be waiting 10 months) i went to the doctors a few days ago and all of a sudden I have an appointment for the beginning on January.. this has me concerned that it could be serious? he uses his legs when laying down (kicks etc) but he doesn't use his left leg in yhe same way and when he did the test where he stroked the bottom of his foot he seemed worried! my son's other development is coming along great and he's hitting all his marks except physical as his legs impede him. anyone have this similar problem with their LO my son is 7 and a half months? thanks