I have had swollen lymph nodes in my neck for years now. i had a ct scan which did not show further abnormalities, but i'm scared i could have cancer?

Need evaluation: Normal ct doesn't prove anything. A doctor should see you and exam all of you and check blood. How many years have they been enlarged? How big and how many? Are there lymph nodes on your exam anywhere else? Do you have sweats, fevers or weight loss? Rash or itching? You should have a further evaluation.

Maybe dental: This is not the likely cause, but if all medical tests are negative, it could be a dental infection. I'd suggest a comprehensive dental check up with x-rays to rule this out.

How enlarged?: The average person your age has three palpable lymph nodes in the neck. If they have been stable, and are not preposterously enlarged (i.e., people aren't saying, "What's that in your neck?"), you'd be doing yourself a favor to go on with your life. If you seem otherwise healthy, the only real concern for serious illness is Hodgkin's and this would be symptomatic by now.