Hi, This is a reflex that you have developed overtime. Formerly therapists used to do psychoanalysis to search the hidden cause in past (childhood) that triggers this. There are other methods of psycho sexual therapeutic counseling that may be quicker in action. Postrema, an area on the floor of the fourth ventricle, has chemoreceptors that trigger vomiting reflex. Stress or some incidence via the central nervous system triggers these receptors. This firing of signals on getting sexual arousal leading to nausea and vomiting can be stopped. Postrema being outside the blood brain barrier medicines can also be used (judiciously) to prevent this vomiting. Self help technique would be to go in the washroom and by inserting finger in mouth induce vomiting. Yog has techniques called vastra dhauti . Learning from Yog teacher also could be beneficial. You can take the benefit of an expert Psychologist or Sex Therapist. Best wishes, Dr. Ashok Koparday