How & what makes the determination that you have ibs? constant constipation unless taking meds & miralax (polyethylene glycol) daily. is this normal?

Normal for IBS: Usually IBS diagnosis is made after normal colonoscopy and no other cause for symptoms found. Here is a website that summarizes the diagnostic criteria for IBS: http://www.mayoclinic.org/diseases-conditions/irritable-bowel-syndrome/basics/tests-diagnosis/con-20024578

Dx of exclusion: IBS is what we call a dx of exclusion, meaning we have evaluated and excluded all other known causes of the symptoms like infection, inflammatory bowel disease, diverticular disease, malabsorbtion syndromes and others. Not normal. Symptom diary and diet diary may shed light on possible link between diet and symptoms. Best to see good GI doctor for full evaluation. Hope this helps. Best of luck.