I have the urge to pee but nothing comes out?

For a couple hours now I've had the urge to urinate. But A few trinkles come out then it just stops. There is also a pain below my stomach. So im not sure if its just cramps or urinate urges. Whenever I press on it it feels like I have to pee but I dont. I have not gotten my period yet because im only 12. Also A few mintues ago my lower back started hurting and ive had these problems for awhile. It will be very helpful if anybody can help me out. Thank you.