Basically, I'm a 17 year old guy and 3 days ago I thought I was fine.

I was with my girlfriend, and everything was hunky-dory, then after she left late my scrotum started to ache from between the testicles and lower stomach, but I thought nothing of it so went to bed. The next morning there was no problem.

The next day I saw her again, but with an hour or two break in between where I felt the same pain. Once she returned it went.

This morning everything was fine again, I masturbated in the early afternoon normally. Then this evening I came in and attempted to masturbate again but couldn't get an erection.

I'm not sure if this is related, or maybe just due to anxiety as I've been worrying about the pain for the last 2 days.

It always seems somewhat strange that I lost the pain while with my girlfriend (but not engaging in sexual acts) and was often turned on by hour.

Can anyone give me any idea what might be the problem?