Male age 26 i had pain 15 days back for one night and vomitted whole night. next day i was alright and no pain till now. doctor says it is appendix?

Appendicitis: Appendicitis can be highly variable in its symptoms from one person to another. Typically it is mid abdominal pain that moves to the right lower abdomen over 24-48 hours getting worse, associated with nausea and not wanting to eat. But not everyone follows the same pattern. I assume you have had appropriate blood testing and maybe ct scan for your doctor to make the best recommendation for you.