Hello, and I hope I can help you today. First of all, if all your pregnancy test last were negative, you are not pregnant. Many other factors can make a woman s period late- some are related to hormones, age, and certain medical conditions. Secondly, regarding your coming and diarrhea- pregnant women frequently can have nausea in early pregnancy, but it should not be associated with diarrhea or severe vomiting. Most of the time, having the symptoms of nausea, vomiting and diarrhea points to a GI illness as the cause. So I recommend you try to hydrate yourself, as diarrhea makes you lose water, and try to eat bland food as soon as you stop vomiting. If you develop high fever, severe abdominal pain or see blood in your stool, you should see a doctor for evaluation. I hope I was able to adequately answer your question today and that my advice was helpful. Best wishes, Dr. Brown