WHat Causes Pain In Back And Testicles?

for like maybe 2 years or so now, not sure my left testicle has been hurting some days the pain is mild, sometimes I don't feel the pain, right now I feel the pain, my back seems to hurt most times, my groin and sometimes my leg feels sore, been to the doctors twice, he said " can't find any lumps you might have damaged it" so I went home a week past pain came, and came back, so I went back again and he says" still cant find anything wrong, he put me on anti biotics a week course, finished them still pain came and went, I didn't go back to the doctors, so was wounding any idea what this is ,I have also seen other people have the same thing as me and doctors can't find the issue