18 years old. swollen lymph nodes that haven't grown in size. but i have a cough and difficulty swallowing followed with chest pains. is this lymphoma?

No way to know: Go see your family doctor. He may put you on antibiotics. You need some blood work and scans done, and if no better a lymph node bx may be required.

Good questions: See the doctor for evaluation. You might need to have some tests done to answer all your questions.

Correlated or not?: It is hard to know, especially without doing a physical exam and taking a complete medical history, whether or not the long standing enlarged lymph nodes (how big?) and your new symptoms are related. If you have not been to a physician, i would recommend going. It is reassuring the nodes have been stable for a year. Further testing, if warranted, can be done to figure out what is going on.