Why does my butt always clench up whenever i dont want it to. This may sound weird but i dont like when my butt clenches up because my penis also lifts up. I have this fear that one day i will do it purposely near people. eveytime like when i wake up my butr clenches randomly when i dont want it too or when im just sitting and i dknt enat it to clench it still does. Is this due to anxiety. How come it only happens when i fear of clenching my butt