Ejaculation not pleasurable

Hi,

I have been experiencing something the last few times I have engaged in sexual activity. I am a 36 year old male and the last few times I have masturbated the feeling is not what it used to be. The buildup to ejaculation is pleasurable, but what used to feel incredible is hardly even noticable now. It really has killed my sex drive because it's all buildup and no payoff. I don't know what could cause this. I felt around on my testicles and may have found a lump on the left one. A few weeks ago, that same testicle I felt "pulse" as if it had a heartbeat. This went on for several seconds and happened twice within a week...then it stopped.

I do not do a testicle check often. To be honest I never have touched that one before, but the loss of pleasure made me investigate. I looked up testicular cancer and do not see my symptom there. I don't know what to do. I'm ashamed and embarrased to talk to anyone, but am afraid of going to the doctor because it might not be anything.

What can I do?

rlyscrd