Frequent Urination, Causes?

I noticed in the past couple of days I have been having very frequent urination. This morning I have peed 5 times since around 9, and they are all very full bladders, like i havent peed all day. I ussually pee around 2-3 times a day, with drinking a lot of fluids. I only drank a half cup of OJ this morning around 11 and then a soda at 230 and i already had to pee at 3. It just seems weird to me. I've been on BC for a month and a week but before i got on it i thought there was a good possibility i was pregnant, but tests said negative and ive been on the pill ever since. What do you think is causing this? its very abnormal for me. Thanks!