Constipation on and off for weeks, gas pains after eating, aching left flank pain with no uti symptoms. cbc/electrolytes and urine tests normal...?

More testing: It is good that Your initial testing has been normal, and suggests a benign etiology. However, you are continuing to have symptoms. At this point, after closer scrutiny of your lab testing, I would consider a CT scan with/or without contrast, to evaluate for other Possible intra-abdominal problems. Additionally, you may benefit, from a GI Sub-specialist Evaluation