Otitis Externa (Swimmer's Ear): This condition is likely due to the presence of a red, swollen, and itchy ear canal, which are common symptoms of otitis externa. The fluid behind the right ear and the red streak on the left ear also support this diagnosis.

Middle Ear Infection (Otitis Media): The presence of fluid behind the right ear suggests a possible middle ear infection, which could be causing the ear pain.
Eczema or Allergic Dermatitis: The itchy and red ear canal could be indicative of an allergic reaction or eczema, which may be contributing to the ear pain.
Ear Canal Irritation or Infection: The redness and swelling of the ear canal could be due to an irritation or infection, which may be causing the pain and discomfort.

Mastoiditis: Although less likely, mastoiditis is a serious condition that can cause ear pain, redness, and swelling, and can lead to serious complications if left untreated.
Cellulitis: The red streak on the left ear could be indicative of cellulitis, a bacterial skin infection that requires prompt treatment to prevent serious complications.
Temporal Arteritis: This condition, although rare in this age group, can cause ear pain and should be considered, especially if the patient has other symptoms such as jaw claudication or visual disturbances.

Relapsing Polychondritis: This rare autoimmune disorder can cause ear pain, redness, and swelling, and should be considered if other diagnoses are ruled out.
Ear Canal Tumor: Although extremely rare, a tumor in the ear canal could cause ear pain, redness, and swelling, and should be considered if other diagnoses are ruled out and symptoms persist.