I have this problem, I'm pretty sure it's mental, in which I simply can't go for a wee unless I'm absolutely busting. I used to be able to. It was mainly in toilets that I'm not used to, like in public. I've had this for years. However, in recent months I've been experiencing it more often in my own toilet. But, I recently got rid of that toilet (against my will) and a new one has been installed. Now, it's a different toilet I simply can't go unless I'm busting, it seems. Not sure what to do about it but it's making me quite depressed.