Why Did I Experience Pain Near The Junction Of The Urethra And Testes, Spreading To My Stomach And Testes, After Ejaculating?

Today I masturbated in bathroom a few (3-5) days later and I ejaculated more semen and then went back to bed and went under blanket and suddenly started feeling pain down there which was concentrated towards the junction of urinary pipe and testes and the pain spread across little bit of stomach and testes as well. I went to bathroom peed very little more white urine and the pain decreased... Why did this pain rise when I had already peed before masturbation