It can vary. In the extreme case, blood will be visible in your urine, and it might even look like you're peeing mainly blood (it's an illusion, but still disconcerting when it happens). At the other extreme, it might just feel like a mild urge to pee, but one that doesn't go away or comes back quickly after you've emptied your bladder. In between those extremes, you might experience something that feels like burning, cramps, or sporadic stabbing pains in the centre of your lower pelvis — especially common at night, when you're still and more aware of sensations.