What is wrong with me?Sick for 4 months with no change!?

Ok so im 15 and ive been sick for months. :( I have sore throat and had strep twice very recently. my last visit to the doc i was sure i had it but she said no ... anywho...i have been sooo tired and sick and sore from coughing but they claim its just sinus' being dumb. Lately ive had stomach pains which i thought were due to gas or something but then it moved to my chest. i get sharp stabbing pressures in my chest a lot recently. I can barely stay awake, stop coughing, sounding like fran drescher (lol) and i have body aches a lot...i just dont think the doctor saw everything. i eat healthy, drink a lot of juice and water, am sporty, etc. any ideas as to what could be wrong?