swollen lymph node on neck for months after having tonsilitus

hi im 17 years old,at christmas i very quickly and very suddenly got tonsilitus,however although i felt extremely ill for 3 days with the usual symptoms of a shockingly sore throat etc,and was so feverish that i couldnt distinguish between my dreams and reality,i recovered remarkably quickly.However since then ive never felt a 100% better,and keep having very small bouts of illness,so small sometimes that they needn't cause worry.However i have also had swollen lymph nodes on my neck now,for at least 5 months. Sometimes they will not be painful at all,and at others they will hurt to touch and cause a sharp pain in my neck. There is also one lump in particular that is constantly there,now all the lumps flare up and down,but this one never goes down so much that it goes away.This lump is on the rightside of my neck,and causes a tension like and aching pain all in my shoulder blade and neck and down my spine. Sometimes the lumps are so bad,on the front of my neck, that they are visible on photographs,although i have had blood tests and tests for luchemia a few months ago but nothing showed up.Im really worried,but should i be??
PLEASE HELP!!!