It could be a urinary tract infection. Those are usually accompanied by some pain or discomfort, but if you drink a lot, it could be keeping it low-grade enough that you don't have pain, just frequency. You might want to consider going to the doctor and getting checked for that.

Alternatively, if the number of times you pee in a day hasn't actually gone up, but you're just *noticing* that you go a lot, it could be nothing but good hydration. If you think you're going more than usual, though, I'd say see a doctor to rule out UTI or any other problems.