Ive had side pain on my left side for 8 days now that also goes up under my left rib at times on my backside (flank) and down in my pelvic region. the pain is not constant and goes away with rest. no uti symptoms. what could it be?

Episodic pain which is relieved with rest is likely from musculoskeletal source. You can try pain pill OTC for a day or two. If pain is relieved with tylenol or advil/motrin, I doubt of any serious issue.

It could be muscul0-skeletal, from the kidney or the abdome- cant be diagnosed accurately without an exam an some tests. Suggest try local heat, Ibuprofen and drink plenty of water If not better in a week or so pl see your doc. Good luck.