What is causing this orgasmic sensation in my testicles?

I'm a 20 year old male and for the past 2 days, my testicles have felt extremely good without any sexual stimulation whatsoever. The feeling might be coming from somewhere else but it feels like it's coming from my testes. Even if I masturbate or have sex, the feeling won't go away. I'm not necessarily complaining but I'm wondering what is causing this. Somebody told me it's puberty but I'm already 20 so I don't think that's true.