I just started having some on and off pain in my left testicle. It isn't unbearable and it just started yesterday. I did donate blood a couple of days ago, not sure if that could have had anything to do with it. I have been on trt for almost a month and have noticed some slight shrinkage in my testicles, no lumps or deformation. On a positive note I am not so tired all of the time, my libido is up a lot, my leg muscles, especially quads, are noticeably harder, and I have more strength in the gym. If anyone has any insight on the testicle pain I would appreciate you sharing it.