Nicola,
The fact that your lymph nodes are painful, is actually a good sign. I kept trying to tell myself that mine (I had 2) were "painful," realizing that usually meant an "infection." Anyway....when my one lymph node took on a life of it's own, and was growing quickly & NOT painful...kind of hard and rubbery and angry (right above my right collarbone)--all the doctors became highly suspicious. Doctors don't know everything--but, the fact that so many doctors believe it to be an infection, is good....although, infections are certainly not fun, either.
Do you have a cat? You know "cat scratch fever" acts like lymphoma. I have 3, and I was SO hoping that might be what I have, instead of "Hodgkin's."
Stay positive & insist on some more tests. As far as what kinds of tests to insist on, I'm not sure. Maybe the more informative ladies on here might have some answers for you.
In the meantime, do everything possible to support your immune system. I've been drinking green tea & I swear, I think it's helping. I haven't started chemo, yet---and I don't think that's going to interfere with it---I'll have to see next week.
Stay positive.....keep seeking.....but, never give up the ship.

Singer