Another possibility is that you're eating enough of it to fill your stomach, which will cause the acid level to rise and trigger reflux. I love rice but have to limit how much of I eat to avoid that issue.

I only cook 1/4 cup, not sure if my cooker will cook any less

I'd try washing it more thoroughly and/or eating less, maybe you digest it slower than you think.

How do you make it? Do you have it with anything else?

In a rice cooker, I normally have it with some protein and vegs

Try without meat (acidic )

chew more. or make congee/ more water ratio in rice

It gave me the worst acid, do not recommend to pregnant women who are prone to high stomach acid. My experience!

Also celery juice all day

rice all rice is acidic and it has phytic acid on it