The liver excretes bile while fasting too apparently and I have certainly had that experience too while fasting. It does feel better after vomitting it up but that doesn't always happen when you want it to of course. The liver can suffer greatly not only due to alcohol abuse but also soft drinks as well. (Just take a look at "SuperSize Me" the movie!) So I think in my case I am suffering with the excess bile from the liver as punishment for my soft drink abuses of late. But I can tell you I prefer the bile to the migraines I was getting before fasting! :)
It is a great struggle getting through that, and I did have to end my first fast because of the bile and nausea due to it interfering with my being a dad. I hope you have better luck getting past this hurdle.