I am having strong stomach pain.feel like vomit.its not continuous pain.sometime come sometime goes.what is the problem?

Lots of reasons...: "stomach pain" can be caused by lots more than an endoscopy can find & may originate outside the GI tract. Further evaluation is in order before anyone can answer "what to do." Your doctor will want to re-examine you as well as know the quality, timing, duration, location, & associations (eating, position, activity, stooling, urinating) of your pain to better direct the next appropriate testing.