The Prevacid may not be working as good as you believe.
Here's my suspicion:
You may already have low acid levels, w/o taking Prevacid.
The main cause of the GERD, Erosive Esophagitis or related condition is mainly LOW acid levels, which cause intra-abdominal pressure increase, pushing the lower esophageal sphincter to open and allow gastric acid to enter the esophagus.
So, It is not even certain that you need Prevacid since any amount of gastric acid, whether you have low levels or high levels, is still going to cause GERD symptoms- burning and pain in the esophagus.
The food should have been long gone by the time you get the burping at night. That indicates that your food may have not been fully digested yet (due to lack of gastric acid) and sitting in the intestines and fermenting, with gas as a byproduct.
Also, if you have low gastric acid, there's a good chance you may have SIBO (small intestinal bacteria overgrowth) which also causes gas, bloating or burping etc.
But, you don't have to take my word for this.
All you have to do is a Betaine HCL trial
(very inexpensive)l, as a test.
Follow the instructions on the label and if it helps and if you feel better, your acid levels are indeed LOW.
To completely overcome GERD symptoms, beyond what I mentioned already, you must consider a better targeted nutritional and dietary approach, but this is another subject.
Please note that my suggestions are not intended as a substitute for medical advice.
There are other possible differential diagnoses to consider, which cannot be all explored here.
Gotta catch some Zzzs!