Abdominal Pain, Loss Of Appetite, Normal Blood Panels, Mouth Sores, Non-itchy Stomach Rash. Any Insight?

Question : Hi. Here is my question. I have been having digestive/bowel issues for quite some time (for at least two years). I often have diarrhea (3-5 significant bouts per month--reminding me in some instances of a bowel prep!) and most often my stools are quite loose; light brown in color and sometimes they looked ridged/or almost triangular. For the past four months or so, I have noticed what look like dark brown or black specks (the size of fine pepper) on the toilet paper after I have a bowel movement. I don't see blood in the toilet or on the stool; but I have developed a hemmorhoid due to the number of times that I go to the bathroom, so sometimes there is a small amount of red blood on the toilet paper. Two months ago I was sent to the ER by my PCP because I had lost so much fluid and was experiencing such abdominal pain. My gastroenterologist suggested a gluten free diet, suspecting an intolerance to gluten which did help settle the constant agitation I had in my lower left side (the blood test for celiac disease came back normal). I have had a colonoscopy a year ago which was normal (except that my colon swings to the right), and my endoscopy (two months ago) indicated gastritis which I took a presciption for. WHen I was in the ER they did a CT scan which also was normal, except that it showed fluid in the pelvic cul-de-sac (I had a full hysterectomy 18 months ago for severe endometriosis) I have lupus and my rheumatologist feels that my stomach issues are likely connected. After one significant bout of diarrhea, my gastroenterologist started me on an antibiotic for SIBO which helped calm things down for about one month (I took the meds for about 2 and half weeks). I have lost a considerable amount of weight in the past eight months (close to 20 lbs with 10 of it coming in the last two months--of which I have put 3 lbs back on). I am concerned about the black specks on the toilet tissue, and wonder if this is blood and if it is something I need to be concerned with. I have completed stool samples (two months ago) and all came back normal. I don't have much of an appetite, and am very tender on my lower left side--which is where most of the pain is contained. I try to eat--but this often leads to emergency runs to the bathroom--sometimes without warning. At one point there was thought that I had Crohn's or other form of IBD, but the blood panels for that come back normal (and the colonoscope seemed to rule out Crohn's). My other symptoms include: sores in mouth (most often along the right side of my tongue) and periodically a rash on my stomach that looks like prickly heat, but does not itch. Any insight you can provide would be great.