Similar to other posts...
Just laying down seems to be my worst trigger. This only started during my 8th month. Today I woke up at 8am with horrible heartburn even though I had not eaten in 10 hours. It got better as woke up and was upright.
The worst I've had was after a meal with red sauce. I was up all night, trying to sleep sitting up and was gagging. I won't eat red sauce again until after I deliver.
Sadly - I'm starting to think chocolate might a culprit too - sigh.
But it's so bad now - that anything I eat will trigger it somewhat - but the above make it much worse.
Zantac helps. I think it's better than popping too many tums a day.