Migraines: The patient's description of pounding headaches, severe enough to cause crying, accompanied by nausea, and blurred vision in one eye, are classic symptoms of migraines. The timing of the headaches, often in the morning, and the presence of abdominal pain and constipation, which can be associated with migraines, further support this diagnosis. The patient's report of general stress and the absence of fever or other alarming signs also align with migraines.

Stress-Related or Tension Headaches: Given the patient's acknowledgment of general stress and the absence of specific stressors, stress-related headaches are a plausible explanation. These headaches can also present with nausea and abdominal discomfort.
Menstrual-Related Headaches: Although the patient's last menstrual period ended two weeks ago, hormonal fluctuations can sometimes lead to headaches. The patient's report of a light period and cramps starting a day after her period ended might suggest some hormonal influence on her symptoms.
Gastroesophageal Reflux Disease (GERD): The epigastric abdominal pain and nausea, especially after taking medication (Tylenol), could suggest GERD, particularly if the patient experiences these symptoms postprandially or in relation to specific foods.

Pseudotumor Cerebri (Idiopathic Intracranial Hypertension): Although less common, this condition can present with headaches, nausea, and visual disturbances, including blurred vision. It is crucial to consider this diagnosis due to its potential for serious complications, including vision loss.
Brain Tumor: Any new onset of severe headaches, especially if accompanied by visual disturbances or other neurological symptoms, warrants consideration of a brain tumor, despite its low likelihood.
Meningitis: While the patient denies fever, which is a common symptom of meningitis, the severity of her headaches and the presence of nausea necessitate considering this potentially life-threatening condition.

Porphyria: This group of disorders can cause abdominal pain, nausea, and neurological symptoms, including headaches. However, its rarity and the specific constellation of symptoms make it less likely.
Mitochondrial Disorders: These disorders can present with a wide range of symptoms, including headaches, abdominal pain, and visual disturbances, due to their impact on energy production in cells. They are rare and would typically be considered after more common diagnoses have been ruled out.