Its been 2 days since i had the sudden strong vomiting and diarrhea (once) ..my question is since that night i havent gone to the bathroom to stool at all whats will be the cause of that ?

After a bout of vomiting or diarrhea, the gastrointestinal system is less active, both in propulsion and in absorption. The body is also likely a little dehydrated. Both of these can lead to lack of BM for several days. Make sure you are rehydrating with water and electrolyte solutions, eat simple, non fatty foods and lots of fresh vegetables and fruits. Your stool will resume soon.

Sounds like you either had a reaction to something you ate, or a short-lived stomach virus. Either way, sometimes a large stool can be followed by no stool as you are recovering. Also, if your appetite has been decreased since that episode, your stool amount and frequency will be decreased. Additionally, you don't need to worry in general if you don't have a stool every day.