Advice please- worried mom

My son is 2. He has two bumps on his neck both sides that the doctor said it’s a “reactive lymph node” they been there for a while now. The doctor also said he is thin and tall so it’s common that lymph nodes stick out more in thinner people. The doctor isn’t concerned and told me to come back in 6-12 months if it’s no different or gotten bigger. And to give me more reassurance to take him to get blood work to get his white blood counts, etc. but they already been there for so long I’m just worried and can’t seem to give my mind a rest. I always thought that lymph nodes aren’t noticeable above the skin and only get swollen/reactive if you’re ill. My mind keeps going to the worse case scenario- cancer. I lost 3 family’s in the last year of cancer so I think the worse.

Any one experienced this with lymph nodes before or any advice?