B.S.
My daughter has had a swollen lymph node in her neck since she was 18 months. My story sounds very similar, she was sick, so they said the antibiotic should clear it up. When it didn't I took her back in, then they said, it sometimes can take longer even after the antibiotic. Took her back in when I noticed another one pop up (but also had a cold at the time). Still said she was fine The new one that popped up did go back down. So at her next well check visit (was shortly after all this) I mentioned it still very much concerned me. Her Dr. still said he felt it was nothing to worry about but for piece of mind for me ordered a CBC. CBC came back normal. He said from this point on I should look for signs of fatigue, fever and or growth of the lymph node or other swollen lymph nodes. She is almost 4 and we still watch it and still have it checked when in at the Dr's She is a ball of energy and not sick very often. From what I've read, the next thing I can do is have it surgically removed if it bothers me that much, but for now I don't want to go that route.
In regards to what LeeLee said, I'm pretty sure the CBC is your next step to check for cancer. So I do believe you're already following the right steps.