You've probably said this somewhere but how long do you shine the light on your testes for? Also how close is the light?
With the light i use, the red light device mini, i hold the light against the skin of the testes for 8-10 min, sometimes for comfort i will place the light .5" -1" away. The light needs to be moved a few times during the session to be able to cover all the areas of the testes, its most comfortable to do this lying down and hold the light between the legs or on a pillow that way you do not have to hold light in your hands the whole time.