How Long Should Zantac Be Taken For GERD?

Hello, I have recently been told that I have GERD and I was not really tested for it I was just in the emergency room and that is what the doctor there told me I had. I have been on Zantac 150 twice a day but nothing is kicking this nausea and bubbling of my stomach. I was never told as to when I should stop taking the Zantac or if I even should.