Zantac for newborns??! HELP! First time mom.

Hey guys... long story short, I recently took my 1 month old to his pediatrician appointment and explained to her that I'm concerned he may have gas issues or reflux issues. By the end of it all and answering her questions, she recommended trying either a probiotic daily or zantac. I opted for the probiotic first because online it says Zantac is only for baby's with GERD... is there a test that takes place to determine if the baby has GERD? I saw a list of symptoms but nothing else... I just don't want to give him something unless he has been properly diagnosed with an issue. Also, if I end up having to give this to him, for how long? I read most ppl say after 3 months this kinda stuff passes.