Pain after long term foreplay

Hi I have a question. I am a 24 year old, and lately I have been experiencing some discomfort after having long sessions of foreplay. The discomfort seems to be in my testicles and goes up to a few inches below my belly button. I noticed that this particularly happens when I don't climax, in other words, when it is just foreplay for say .. 2 or 3 hours.

Help me!!!