It is possible that you may have a food intolerance or sensitivity that is causing your stomach pain and immediate need to go to the bathroom after eating restaurant food. It would be helpful to keep a food journal and note any symptoms that occur, so you can identify any potential triggers. If the problem persists and bothers you, it would be best to make an appointment with your family doctor to discuss your symptoms and possible causes. They can help you determine the underlying issue and provide appropriate treatment if necessary.