Left groin pain and lower back pain

I’ve been making pain/discomfort around my left testicle, the pain feels like it’s coming from the i inguinal canal. I’ve been having this pain for about 2 years, it comes and goes. The pain also radiates to my lower left back. When I change my sitting position to find the right one, the pain goes away. However one certain days it doesn’t work.

Moreover I went to the hospital a year and a half ago, the urologist did a invagination test (where he sticks a finger inside the a part of the scrotum) on the left testicle and I did feel the exact pain when he did it: I d see id an ultra sound after and nothing turned up, so I was just sent home without much. But the pain never went anyway. The only symptoms are left groin pain, sometimes right, some both sides and lower back pain. So what might be the cause of this?