Hi rubenesque
Sounds like you need to have that baby soon
Need to know a bit more here...
You say you have been taking 12,800 mg calcium carbonate per day. In what form? The Gaviscon (liquid form) available in Australia also contains calcium carbonate...?
Acid reflux at this stage of pregnancy is all physical, and the good news is you should not have any of these symptoms at all in about a week or so

. Gaviscon is by far the best medicine for this condition as long as it is taken correctly. You need to eat, stop eating, then top it off with a dose of Gaviscon -
after each meal (this is really important)
and at bedtime. Gaviscon contains an ingredient called sodium alginate which actually gels to form a "raft" on top of the stomach contents - therefore stopping any acid shooting back up the oesophagus.
I know you are watching the things you eat - also watch the quantities. Go for more earlier in the day and less in the evening. The other thing to try is propping yourself up on pillows to sleep - as high as you can manage - gravity is a good thing when it comes to reflux.
Hang in there. I feel for you (my Gaviscon pregnancy advice is from experience) and best wishes for the birth.