Everyone with sexual obsessions (and even some with harm obsessions) have dealt with this - if it helps at all, the part of your brain responsible for arousal doesn't really separate excitement & fear (as in, the brain treats them the same.)
Groinals happen because we don't want them to - we're scared of them, thus making them a perfect target for OCD. Try and not ruminate on it, or reassurance seek, or whatever other mind tricks your OCD wants you to play. A thought or a feeling aren't actions - we don't control our thoughts or feelings, only our actions. Remind yourself that.