Pain In Left Testicle During Masturbation

Hi,

i'm a 22 year old male. Two weeks ago after masturbating a couple of days in a row (never more than once a day), I started feeling some pain in my left testicle that I had not experienced before. The pain is not present during normal unerected or erected state, but starts appearing when I actually masturbate and reach a stage of excitement. It disappears a couple of minutes after ejaculation or if I stop masturbating. I've took a five days long break from masturbation, but when I recently tried it again, the pain still appears. My sleep has been a bit unstable lately (not getting enough), and i've been training some. I'm circumcised and have been masturbating a couple of times per week since my early teens.

Thanks,
hannes