I have enlarged lymph nodes at least twice a year lasting 6-8 weeks with fatigue and joint pain. ultrasound last year normal. should i be concerned?

Yes: Fatigue and joint pain can be serious and related to a joint issue such as rheumatoid arthritis. Lymphoma can be associated with enlarged lymph nodes. Other diseases such as sarcoid could be possible. You maybe just have the flu on a fairly regular basis. I would see your family physician about testing for any conditions that could cause these findings. A referal to a rheumatologist maybe needed.