I was 35 weeks yesterday and it's so bad I can hardly sleep at night it keeps waking me up, so I'm watching with interest.
Ranitidine helped me for a few weeks, I was taking one a day then two a day now they just don't seem to work anymore, I think I've become immune (they're 79p a box in b&m bargains but I think they're the prescription version of Zantac)
The only thing that seems to be helping lately is Asda and tesco heartburn and indigestion liquid, it tastes vile but does really help x
Ask your gp/mw to prescribe something - I had two different types of heartburn stuff prescribed - I can't remember what it was called but the most effective one was a chalky liquid you mixed with water. Also sipping cold coca cola.
I second daffodil. Omeprazole was like a magic pill. One minute it was there the next gone. Ask your GP for a prescription. I was already downing gaviscon 4 x a night at 24 weeks and then 1 tablet a day and the heart burn went. It was recommended to me by my pharmacist DSis who double checked that it's absolutely fine to take in pregnancy. DS is now 1 month old and happily all traces of heart burn are now gone!