Lymph nodes swell and go down for last 3 months all blood tests normal, should i be worried about cancer? no cancer runs in my family.

Concerned: Transient swelling of the lymph nodes(or lymphadenopathy) that resloves completely is not alarming. Difficult to assess what 'all blood tests normal' entails; however you should let your doctor examine you...And periodically perform surveillance to ensure that your lymphadenopathy is not the harbinger of something worse. "cancer" is so wide ranged a topic i require more details before i comment.

Unlikely: Cancerous nodes are unlikely to alternatively get smaller and swell again. This sounds more like an allergy, local irritation or infection. Does your skin away from the enlarged nodes have area that's red or cracked or irritated? Any recurrent viral illnesses? A biopsy may be necessary to get to an answer.

Steroids used?: Enlarged lymph nodes caused by cancer do not spontaneously shrink, so my likelihood of suspicion for cancer is very, very low based on the limited information provided. That being said, were you treated with any steroids during this time (prednisone, dexamethasone, etc.)? Steroids can partially treat leukemia/lymphoma for a short time, and then the cancer comes back and is more difficult to treat.