Hi,
All these symptoms, on the back ground of 
smoking, too much caffeinated drinks and night shifts may suggest 
gastritis or 
peptic ulcer disease. It will be fine if you can have a sitting with your doctor for initial evaluation. If confirmed, this will respond to acid suppressants alike 
pantoprazole and antacids for few days.
Meanwhile, try cutting down cigarettes and caffeinated drinks, as both these increases acid secretion in stomach and worsens symptoms. Also, avoid spicy, fried, hot items. Include plenty of fruits and green leafy vegetables in diet, drink enough water. For 
weight loss, it is better to have 3 healthy meals(low in calorie and fat) rather than one large meal. Also we have to cut down caffeinated drinks and snacks, as all these are rich in calories and adds to weight gain. Try having regular exercise at least 45 minutes a day.
Regarding menses, if no bleeding in 2 weeks of expected date, just get a urine 
pregnancy test done to be sure. Otherwise, it may be from a transient 
hormonal disturbance, which can be precipitated by an intermittent stress or illness
Hope I have answered your question. Let me know if I can assist you further.
Regards,
Dr. Muhammed Aslam T. K., Pediatrician