Hi..
Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concerns..
As per your complain and presentation of symptoms nausea and diarrhea along with black stools indicates 
stomach infection and rise is temperature is due to infection from stomach entering blood stream and body tried to wall off the infection leading to rise in temperature..
The 
swollen lymph nodes are due to the generalized infection that has caused Reactionary 
Lymphadenopathy causing swollen painful lymph nodes..
Nothing to worry take a short course of antibiotics like 
Metronidazole..
For heart burn take antacid like 
Milk of Magnesia..
Take furozolidone (lomofen) tablet for loose motion..
Avoid hot and spicy food..
Take more of Probiotics like Yoghurt..
Drink lots of water to maintain hydration..
You can do cold compresses over lymph nodes for reducing Inflammation and swelling..
Hope this information helps.