Tension Headache: This is the most likely diagnosis given the description of the headaches being painful on the temples and behind the eyes, improving with Tylenol, and being relieved by rest. The symptoms are classic for tension headaches, which are common in young adults and can be exacerbated by stress, lack of sleep, or other factors that might be present in a new mother.

Migraine: Although the patient mentions the pain is better with Tylenol and improves with rest, which is less typical for migraines, some migraine sufferers may experience relief with over-the-counter pain medications. The location of the pain (temples and behind the eyes) could also be consistent with migraines. The fact that the headaches sometimes wake her up could suggest a migraine, as migraines can be severe enough to disrupt sleep.
Postpartum Depression or Anxiety-related Headaches: Given the patient's recent childbirth, it's possible that her headaches could be related to or exacerbated by postpartum depression or anxiety. These conditions are common and can manifest with physical symptoms such as headaches.
Sinus Headache: If the patient has a history of sinus issues or allergies, her headaches could be sinus-related, especially if they are accompanied by other symptoms like facial pressure, nasal congestion, or fever.

Preeclampsia: Although less likely given the timeframe since delivery, preeclampsia can occasionally present postpartum. Severe headaches are a symptom that warrants investigation for preeclampsia, especially in a recent postpartum patient.
Subarachnoid Hemorrhage or Other Intracranial Hemorrhage: A sudden, severe headache (often described as "the worst headache of my life") could indicate a subarachnoid hemorrhage or another type of intracranial hemorrhage. Although rare, this is a medical emergency.
Temporal Arteritis: This condition is less common in younger individuals but can occur. It presents with headaches, often temporal, and can be accompanied by visual disturbances, jaw claudication, and fever.
Pituitary Apoplexy: A rare but potentially life-threatening condition that can cause sudden, severe headache, often accompanied by visual disturbances and altered mental status.

Idiopathic Intracranial Hypertension (IIH): Also known as pseudotumor cerebri, this condition can cause headaches that worsen with recumbency and can be associated with visual disturbances. It's more common in obese females of childbearing age.
Cervicogenic Headache: Originates from the cervical spine and can refer pain to the temples and behind the eyes. Less common but should be considered if there's a history of neck trauma or strain.
Trigeminal Neuralgia: A rare condition characterized by sudden, severe, shock-like pain around the eyes, lips, or nose, typically on one side of the face. It's less likely given the description but could be considered if the pain is extremely severe and localized.