Since January i have been sick every 3 weeks. I have been to ENT, Pulminary doctor, had MRI of lungs and Sinus, did the breathing test for asthma and had a TBI test. I constantly have had a cough for over a year and a half. It seams like every three weeks, my lymph nodes on the left side of my neck get really swollen (this is new to me this year). I dont have a temperature. I just get really stuffed up, tired, my cough get worse, sore throat, chest congested but nothing really comes up. Even went out of my house for a week on vacation..and got sick in that environment. SO, what could this be? What is causing my immune system to be so low that i have to go on antibiotics every 3 to 4 weeks? I had a HIV test ...it came back Neg. I took a allergy blood test and that came back NEG. Is this allergies? Do i need a scratch test?