A doctor suggesting to give juice to an infant of any age is a doctor I would not go back to, period. Especially a child so young. That is not good medicine, IMO.
My first son was not gassy, my 2nd horribly gassy. My first didn't spit up, the 2nd did a little. Neither would ever take a bottle without a fight, ever. Smart these BF babies are, who wants a bottle?