Torsion is usually an acute condition characterized by severe pain- the testis undergoes a rotation on its pedicle compromising blood flow to itself.
In the absence of a palpable lump, cancer seems to be an unlikely cause of your problems; a sonography of the testicles can be of some help in identifying tumors that are not detected by physical examination, also tumor markers, measured in the blood sample, can be of use. These are generally ordered only if the index of suspicion is high.
Chronic testicular pain can just be an idiopathic finding- without any identifiable cause. treatment is usually symptomatic (analegesics, scrotal support etc,)
Doc you didn't answer my question about penis pain!!