If your doctor gave you Zantac to take at night, I suspect he/she means at bedtime. When my reflux was at its worst, my doctors had me on PPIs before breakfast and dinner, and Zantac (300mg) at bedtime, to try to stop reflux while sleeping. (lying down makes it easier for reflux to migrate into the esophagus. Has anyone suggested elevating the head of your bed to help keep the acid in your stomach via gravity? Putting bed risers or blocks under the legs at the head of your bed and raising it 7-8 inches, can be very helpful.)
If your doc said you can take the Zantac more often if needed, then I suspect it means to take it at mealtimes. I suspect it would be a good idea to take if you are eating something that generally causes problems. With Zantac, you can take it with food, or even after eating the offending meal. PPIs are different, and have to be taken an hour before meals on an empty stomach.
Here's a great general GERD resource you might find helpful:
Good luck! Hope you find relief.
Nissen Fundoplication 2/09
"Whatever you fight, you strengthen, and what you resist, persists.”
“Worry pretends to be necessary but serves no useful purpose”
“Accept - then act. Whatever the present moment contains, accept it as if you had chosen it. Always work with it, not against it.”