Hi ! You have not mentioned the site of pain in your stomach/abdomen. However, the way you have described your symptoms and signs, possibly you have a sub acute attack of appendicitis
, where you got nausea
with mild fever
which caused you a headache.
You did not have a diarrhea
, which is not favouring a food poisoning
With all probabilities, the sub acute attack has caused the omentum to seal it off with a localised inflammation of peritoneal cavity
and a appendix
mass formation, which gave you a weired feeling on touching. This can give rise to pain and tenderness on moving, coughing or sneezing
or any work where intra abdominal is altered and the inflamed perietal peritoneum
is distubed. In my opinion, you should take the opinion of a general surgeon
by getting clinically examined in person, who may also advice you for some blood and radiological investigations like ultrasound
If it proves to be appendix mass, then you may have to be admitted in the hospital for IV drugs, and other conservative management, and the surgeon may advise you for an interval appendicectomy. Get yourself seen and investigated by your doctor at the earliest possible. Good luck.