Yes Thank You, I Have Had Severe Testicle And Lower

Yes thank you, I have had severe testicle and lower left back pain for over a year now and I can't figure out what is causing it.I went to the doctor numerous times and have had many tests done,blood test,urine test ultrasounds,and they have come up negative on all tests.I have excruciating testicle and lower back pain especially after a bowel movement, can you pinpoint or maybe have an idea as to what is causing this very uncomfortable main pain?