I understand about the nausea. I used to get nauseous after every meal! I didn't do a parasite cleanse before my first flush, and I did get very nauseous in the middle of the night on my first flush. It was so bad that I wondered why people would put themselves through it time after time. But my body had big work to do that first flush. I expelled a major blockage in the neck of my gallbladder. I never get nauseous anymore, either when I eat or when I flush. A little discomfort for a few hours is SO worth it in the long run!
I have a suggestion for you that might help. There are different brands and grades of olive oil. I have found that Olio Beato makes an extra virgin olive oil (organic) that is mild in flavor, and it may make all the difference in getting it down successfully. It is pricey. I think I paid $12 for 500 ml (17 oz.), but I feel it's worth every penny. And you can order over the internet if you need to. (see link below). I found mine at my local health food store. You might also try a different kind of oil, such as walnut or almond. Anything is worth a try if it will save you from surgery and future problems.
I hope you will not give up one "try" too soon! You just might have success next time!!