Benta: It's no doubt from the decreased blood flow. What kind of cool down have you been using? You may want to try mixing heat with cold after a workout, sort of how like the discussion in
this thread. It's relatively new and uncharted, but I've tried it a few times and it seems more promising then doing just one or the other.
Dustpan might have some better answers on this one than me. He's more experienced with the cool down. Dust, did your penis turtle up as well after your cool down sessions?