Hi anan,
Welcome to HealingWell!
I'm assuming your doctor ruled out GERD when you got scoped? Too much acid production can definitely cause nausea. Also too much iron. Aside from sodium and calcium, did your doc do any other blood work? If you are on a multi-vitamin you might want to stop taking it to see. I think an abundance of vitamins A, E, & C also cause nausea.
Can you find any ginger tea in Singapore? If not, lots of other teas can also help with nausea. What about
the internet? Can you buy ginger tablets on the internet????
I have not tried Digestrol, but I believe a few people who frequent this site have. Hopefully they'll be around shorty. Almost all of us on this site take some sort of probiotic. I take supplements (Culturelle & Kyo-Dophilus), I eat Dannon Activia daily, and I used to take 'Digestive Advantage for IBS'. All really help with gas, nausea and regularity.