Lymph nodes on lower back?

Hi all, would like to know if anyone has experienced swollen lymph glands across the sacrum/ilium? 

History: 2 months ago I discovered a firm lymph gland in my right armpit. After antibiotics (which did no good) I had a mammo, which showed swollen lymph glands in my right breast, which I can feel. Doctor says this is normal. Today there are three in my right armpit and one in my left armpit.

2 weeks ago, I felt a bunch of swollen lymph glands across my lower back. Doctor assures me this is actually pulled muscles, and not to worry. Having had pulled muscles, I imagine a load of knots (fits into the palm of my hand) would make it impossible to walk/stand/whatever. All of the swellings are painless.

All the labwork appears normal (except lactase dehydrogenase, LDH) which is elevated, as "expected" by the doctor.

i can find nothing regarding swollen lymph glands across the lower back, have been told this "is impossible," yet there they are. Have been patted on the head and told not to worry, been placated by nurses who told me that my diagnosis is benign, based on biopsy, which I have been fighting to get for two months.l

I'm starting to think I am imagining this. Or that I'm making a big deal out of nothing. 

Has anyone had a similar concern?