UTIs can be caused by bacteria, viruses, fungi, and even parasites. Avoid sitting around in wet bathing suits and hot tubs - these breed germs.
Drink real cranberry juice and lots of water, could be a bladder infection (quite common from a hot tub), take Tylenol if it gets painful not ibuprofen.
If this continues, I recommend seeing your family doctor to make sure this is nothing serious. There is not enough information given that will let us know exactly what is going on.