I am the same as Sparkle. The two times I had it worst where 1) The same day I had my oestrogen measured which at the time was 40pmol (so v low) and 2) when I moved to a very high dose of synthetic oestrogen. From this, I can only conclude that it is either 'extremes' or fluctuating hormones, rather than high or low per se, that cause my nausea. (A lot of people think it's just high oestrogen that causes nausea, but for me at least, I know this is not true).
Totally separate to this, I can get a different sort of nausea when my digestive system is misbehaving and I am full of air/gas. I get this horrible feeling of nausea until I burp a lot and it calms down (sorry, tmi!).
As for things that helped, both Milk of Magnesia and Pepto Bismal (sp?) did a bit. Motillium was great but is now discontinued. I am about to start Bioglan Biotic Balance Ultimate Flora Capsules which have good reviews.