I Have Been Sick For 16 Weeks Now. I've Been

I have been sick for 16 weeks now. I've been to the doctor 3 times and have had three antibodies. Each time I feel somewhat better for about 3-4 weeks and then I'm back feeling the same. Symptoms are: chills, achy, cough, chest tightness, loss of appetite, and very tired. I've had 8 vials of blood drawn for numerous tests and xrays but all are normal.