My dear, that's acid reflux! I am actually taking Zantac for mine, as prescribed and OMG do I feel better! It's not your regular heartburn, see - it's rather different and you really want it to stop because actually, you can aspirate on what comes up if you don't wake in time (which actually almost happened to me) and contract things like pneumonia - no lie! I lived with this for several weeks before finally telling my doc I'd had rather enough of the "heartburn" - well, since I've been on Zantac it's just 100% better. Really.
I know, it's miserable. Regular Tums won't touch it - milk seemed to help me slightly in the night, but it didn't stop the sickness, which was miserable. So my rec is perhaps to take Zantac twice a day. It's okay to take in pregnancy and will allow you to actually sleep, which is rather important when making a baby!!!
*HUGE hugs* XXX