What Causes Lump Just Above The Pubic Symphysis And Left Of Midline?

I'm 35 y/o female (63" 140lbs) with one twin pregnancy 5 years ago, delivered by c-section. I have a lump just above my pubic symphysis, and just left of midline. I found it a few weeks ago and had it evaluated by my primary about a week later. It is hard, not tender, not reduceable, not moveable. A quick u/s by a friend revealed that it was not a cyst, or hernia, or even scar tissue. She has not yet finished her report from eval 9-9, and now it's 9-12 and the lump has grown from the size of a finger tip to the size just larger than the end of a thumb tip. It was oblong up/down, now it's oblong laterally. I have history of endometriosis, undetermined source of dysfunctional uterine bleeding, IBS, pre-cancer colon polyp, and ovarian cysts. I have looked online to see where pelvic lymph nodes are, and I'm having trouble. Could this be a lymph node?