Bleeding Stops While 'turned on" / or "wet" While On My Period?

 I've noticed that while on my period if I'm gettingn turned on or wet, I stop bleeding even though I'm on my period. Sometimes there is a little blood but not much, (like the size or amount of my fingernail) and I only start bleeding again until after I'm not "in the mood" anymore. 
 Does anyone have any idea why this happens, and is there anyone else this happens to? Feedback would be much appreciated! 
( I'm a sixteen year old female normal height and weight. I've noticed this happening for about two years now.)