Epididymis is rock hard after ejaculating

I notice that at times my epididymis is swelled up and hard. This happens from time to time. It happens daily first thing in the morning and always happens after ejaculating. Iv'e seen a urologist who put me on medication for epididymitis, but nothing. It doesn't appear to be an infection. There is usually a slight ache when this happens but at times goes unoticable. Any suggestions?