I vomitted on my very first flush. That was also my most successful flush. So I lean towards the theory that your liver is very congested. I also agree that you should lower the dose of the mixture. It is obvious that your body requires less to activate the gallbladder to relase all that bile.
I also hate grapefruit juice, always have. Another juice might help, like others have said.
What are your medical problems? Do you normally have stomach trouble or reflux? If so, perhaps you have an ulcer.