You should see your doctor..this is not a psychiatric, but a physical problem.
I'm not sure. It could be a gastro thing. It could be food poisoning. It could be a virus.
The breast tenderness can be a symptom of menstruation but it sounds like it could be more of a reflux thing (heart burn) due to the vomiting.
Basically, I have no idea so you need advice from a doctor.
I would probably try and take fluids but if you feel no better and become dehydrated I would see a doctor.