Tales from the tiny bladder

I'm not kidding when I say I have a small bladder. I'm currently on the same pee schedule as a very heavily pregnant woman in my office. I've seen her about three times this morning. She's also senior management, so she must think I'm slacking off, going to the toilet as often as a heavily pregnant woman does. 

Here's the question: How do I tell senior management that I'm not slacking off, I've just got a really tiny bladder, without sounding like a complete idiot? 

Life is so hard.