Strep Throat (Acute Pharyngitis): This is the most likely diagnosis given the symptoms of strep throat for 2 weeks, which can sometimes be accompanied by neck pain due to lymphadenopathy or inflammation of the throat.

Mononucleosis (Infectious Mononucleosis): Caused by Epstein-Barr virus, it can present with sore throat, fever, and lymphadenopathy, which could explain the neck pain.
Lymphadenitis: Inflammation of the lymph nodes in the neck, which could be due to a bacterial or viral infection, and could be related to the strep throat or a separate infection.
Peritonsillar Abscess: A complication of tonsillitis where an abscess forms beside the tonsils, which could cause severe throat pain and neck pain on one side.

Lemierre's Syndrome: A rare but serious condition that starts with a sore throat and progresses to include neck pain and swelling due to a thrombophlebitis of the internal jugular vein, often caused by Fusobacterium necrophorum.
Retropharyngeal Abscess: A serious infection in the tissues in the back of the throat, which can cause severe neck pain and stiffness, and can lead to airway obstruction if not promptly treated.
Epidural Abscess: A collection of pus in the epidural space surrounding the spinal cord, which can cause neck pain, fever, and neurological symptoms, and requires urgent medical attention.

Tuberculous Lymphadenitis: Although rare in many parts of the world, this condition can cause chronic neck pain and lymphadenopathy, and should be considered in patients with risk factors for tuberculosis.
Neck Tumors: Both benign and malignant tumors of the neck can cause persistent neck pain and should be considered in the differential diagnosis, especially if other symptoms such as weight loss or a palpable mass are present.
Actinomycosis: A rare bacterial infection that can cause chronic inflammation and abscesses in the neck and throat area, often related to dental problems or oral surgery.