Should i be concerned about swollen glands in my 15 year old son?

My son has been feeling unwell for the past few days with cough, headache and lethargy. went to Dr yesterday morning and she said it seemed flu like but today he has swollen glands in his groin and neck and stomach pains. he has been sweating far more than usual but has no high temperature. he also discovered a Cyst like spot on his penis today so i am a bit concerned but he isn't keen on going back to Dr. is this all likely to be a reaction to an infection? i have never known him to be this lethargic.