Look, I am no dr. at all, I can tell you what I have done.
There is a test you can ask your MD for, is a Comprehensive Metabolic Panel and you can ask for a "Candida Antibody, ID"
If you do so, be aware that these test are not 100%, from what I've read, they say they are %70 reliable.
But if your GERD began with anti-biotics you could have messed with your intestinal flora. Meaning your good bacteria may be out of sync. You can look into probiotics, see if it helps.
I've tested for Candida with an MD and with special labs that, are trained in parasites, fungus, bacteria,and viruses. Like I said in the previous post, it can be a myriad of causes. From what I learned, taking too many anti-biotics is not good. There are quite a few ppl who's GERD began after taking anti-biotics, maybe they can share something with you.
You can also test for h pylori with your MD, but try to get a Breath test or stool test unless you never tested for it, then you can do the blood test.
Write down the test and see if your MD can work with you. Like I said, the things I am telling you, are from what I have done or experienced.
Look into candida-diet if YOU feel is candida but also know that your MD will probably rule this out immediately or will not be interested in testing for it. It happened to me, I had to convince my MD, to test for it. Then I realized, I could test for it more accurately at a special lab. Anyway, keep me posted.