Thanks for posting your query at DoctorSpring.com
I have gone through your question in detail and I can understand what you are going through.
You have excessive thoughts about the dirt and and the resultant nausea and vomitings. Your vomiting center in the brain is over sensitive to the obnoxious stimuli. We need to do two things.
1. We need to control your thoughts about the dirt and filth. These uncontrolled thoughts could be a part of obsessive compulsive disorder. This can be controlled with systematic desensitizations with relaxation. This is a behavioural therapy done by a clinical psychologist. Further among medicnes 60mg of fluoxetine or 50mg of fluvoxamine may help to reduce the thoughts.
2. We need reduce the sensitivity of the vomiting areas of brain. This can be done by taking medines like ondansetron daily for a few days while you are doing your behavioural therapy.
This may require 6-7 sessions and I would advice you to visit a clinical psychologist for this purpose. He will help you with the behaviouaral therapy sessions.
Hope this helps
If you have any further query do let me know.
Dr. Srikanth Reddy MD