You are being treated for heartburn or hiatal hernia, and you feel sudden chest or stomach pain, have difficulty swallowing, are vomiting, or are unable to have a bowel movement or pass gas; you may have a hernia that has become obstructed or strangulated, which are emergencies.
One strong possibility for your symptom is gall bladder stones and cholesterol deposits within the gall bladder which can cause sharp pain. Getting an ultrasound of the upper abdomen done in a walk in clinic or the ER will confirm the diagnosis.
Striking the patellar ligament with a reflex hammer just below the patella stretches the muscle spindle in the quadriceps muscle. This produces a signal which travels back to the spinal cord and synapses (without interneurons) at the level of L4 in the spinal cord, completely independent of higher centres.