If i had a cbc and chest xray in december and they were clear, should i be concerned of swollen lymph nodes in my neck? what could be causing them?

Lymphadenopathy: Many possible causes. If a doctor finds them significant then the best means of diagnosis might be biopsy.

Investigate: Swollen lymph nodes can be from a variety of causes. They can be relatively benign, as a reaction to throat irritation or infection, you do have sinusitis, or they can be symptomatic of a growth somewhere in the head and neck region, or elsewhere. They can also be a reaction to systemic issues which are accompanied by lymph node enlargement. Get with a doctor and track it down if it persists.

Lymphadenopathy: Multiple enlarged lymph nodes in the neck can be residual of a viral illness but they should shrivel over time. In my experience this is more common in younger patients. In adults, if they don't recede or if they enlarge further a biopsy is often done to see what the pathology is. A normal CBC and chest xray isn't enough to rule out some diseases. Follow up with your md.