I can’t help but feel like you’re kind of getting yourself stuck in a self-fulfilling prophecy here. You get a random diamond cutter event that’s just your nervous system doing a systems check since you usually have a go around this time, it freaks you out, and from there you locked yourself into a “don’t think about pink elephants” situation until you’ve reinforced your body’s assumption that hey, this is usually diamond cutting time, get to it. Maybe a sex therapist can help you out here, but if they can’t, there’s no shame in hiring someone to take care of that the other way.

Squeezing your thigh/butt muscles will make it go away. (I've heard)