there could be several explanations to your nausea. The most plausible and common reason is that the amount of oil is to big. Try to cut down the amount of oil a little and see if that helps. Or divide the dose in two and take them one hour apart.
I felt less nausea when I started adding a little ginger in my flushes. Peppermint an hour after the flush helps too. (I noticed that if I mixed the peppermint in the oil, the flush always was less successful. But if you wait till at least half an hour after the flush it will probably not interfere with the results.)
It could also be that you are a little sensitive to the olive oil. (I am) Then it could be a good idea to avoid olive oil in between the flushes. Then the reaction will not be so strong when you flush. Or maybe try another oil.
If you vomited several hours after the flush it shouldn't affect the results. But I don't think a congested liver make you nausea.