I Have Swelling In My Right Lower Abdomen Haven't Had

I have swelling in my right lower abdomen haven't had a bowel movement in two days went to emergency last night had blood work came back negative had a CAT scan came out clear was discharged haven't had a bowel movement today taking a probiotic produce lots of water obvious swelling I also have back pain but I think that's the contributed to the swelling in my lower right abdomen any ideas