Lower posterior pain, tested cynical for urinary track infection, what else could it be?

I was experiencing lower posterior pain and I go to Urgent Care (and the ER) they tested me for a urinary tract infection, both turned out negative. The misery however is worse lately and is more like a pinching niggle, that hurts really bad, but it is sharp, comes fast/leaves fast. I haven't lift anything heavy. I've also be haing abdominal pain, go to the ER for that, they tested me for gallstones (did an ultrasound), and it was denial. All these pains are driving me crazy! I am always scrawny and lack vivacity too!
Answers:

Does your back hurt after an epidural?

Did they look for appendicitis, endometriosis, sciatica? So masses things can cause this humane of pain. Fibroids could also incentive symptoms like these.

Bacterial Vaginitis/Vaginosis Won't Go Away?

Stop screw around and get to a specialist. And if he have no clue, then travel to another one.
This is your life we're chitchat about. Just because you go to a"Dr." isn't gonna mean squat if you hold something serious like cancer or something else.
Believe me very soon or believe me later...You HAVE TO MANAGE YOUR OWN HEALTH CARE! No one else is going to do it for you. I know from experience.
May God Bless You