Hi, I am having pain in my lower left-side stomach area that seems to be coming from the kidney are

The pain seems to be from my kidney area and works around to my lower stomach on the left side. I am a kidney transplant receipient of two years and nothing seems to be wrong on the right side where my new kidney is. But on the left, everything seems to be wrong, I am even more muscular on the left side. I believe it may be an ulcer from the research that I have done. Some say, Acid Reflux, but why only on the left side. An ultrasound gave no indication of anything wrong. A pap smear cleared a female problem and a urine test shows no indication of infection. Blood has been in my urine and bacteria shown from tests. An antibotic eased the pain for awhile, but now it is back. No one seems to know what is wrong, but I know it is something wrong. Please help me to at least get in the right ball park. Thank you so much.