Hi Ali,
so sorry you have had to join the club no-one wants to join.
I can relate to what you are saying, at least in part. I was told at diagnosis (dx) that I had one enlarged lymph node. I had chemo (FEC-T) then a mastectomy and lymph node clearance. The pathology showed three affected nodes.
You ask if this is 'bad' and I suppose the answer is 'yes and no'- obviously we would prefer not to have any cancer in our lymph nodes, but if there is, then it actually shows they've done their job of stopping the nasty cells getting any further. The anantomy and physiology is complex, but basically most people have some sentinel lymph nodes, so-called because they act as sentinels or guards to catch any stray cells before they could escape and go elsewhere. If they find cancer in sentinel nodes they will often/usually take all the nodes away and check them too.
Many hospitals give rads to people with lymph node invovlemnt - I had three field rads, much as you describe, and my onc was quite clear that this was precautionary in case there were any stray cells which could not be detected otherwise.
I am now a year on from the end of treatment and fit and well, enjoying life and generally happy. Hopefully the same will be so for you.
If you are worried, then maybe either speak to your breast nurse or try the helpline here - they are excellent.
Take care and hope you get some reassurance soon.