How can I take my mind off needing the pi*s in my exam?

Hey guys, I think ive got some sort of bladder infection as I need to do a pi*s every 45 minutes or so. My dad says its mostly a mind thing and hes right, if I dont think about it I dont notice it. But Ive got an exam later today and I know that im probably going to need it, and I dont want to ask as everyone will probably be staring at me when I go off to the toilet... The more I think about it, the more desperate I am, one time during another exam I thought right at the beggingin that im going to need it, then by the end of it I was ******** bursting for it! I just need a method of not thinking about it... and I need to focus on the english paper... please help!