Pain in my perineum (area between testicles and anus)?

I am a male, and I have recently been to the doctors before this began for an STD test, but I came up negative. But for about the past 3 weeks or so every time I orgasm, It hurts really bad right in front of my a**hole, where the muscles contract. With each wave of orgasm is like another wave of pain, lol. But yeah, does anybody know what this could be? Thank you!