I've been using the bathroom like crazy, literally every 10 or so minutes. It doesn't matter if I drink water constantly or if I barely get my recommended amount. I thought I had a bladder infection but I've had a urine test and am completely clear of and by sign of it. I'd still mention it to your doctor if you're concerned but I wouldn't necessarily worry about it.
Could be a uti. The cramping could be bladder irritation and the increased urination would also point to an infection. I would call the doc tomorrow and have them check your urine just to be safe.