Where Can I Get A Thorough Fecal Test To Evaluate Possible Infection Or Parasites Causing Rectal Irritation And Radiating Pain?

i need to know where i can go to get a very thorough fecal test for joint pain along with rectal irritation. Need to know why i am getting this pain and goes to my lower back and legs. I do Not have hemorrhoids. Do not need a colonoscopy. I feel like I have bacterial infection or parasite or something going on in my rectal area and then it starts spreading misery to rest of my body from lower back to ankles. would a neurologist or endocrinologist help? This has been going on for 6 years & no one seems to help me. Have had back surgery & total hysterectomy for large fibroids but not the cause of my problem.