Years ago i lifted a heavy load, since then i started having pain on lower back and abdomen, testicles pain came some weeks later. what can it be?

Inguinal hernia?: It is possible that the back pain is a separate issue or referred pain from the testicle, you should be evaluated to see if there is an inguinal hernia or any other cause for tis pain.

Back problem or: Hernia. You could have a disc problem in your back. That would show up on an mri. It could radiate into the abdomen and testicles and could occur after lifting a heavy load. A hernia could mimic those symptoms also.