What Causes Tightness And Discomfort In Bladder During Urination?

Hi quick question I have had kedney stones like every other month for the year of 2014 so it's been over a month and for some reason I feel like after I pee like I still need to go like its sitting right were my urithra is but can't come out I mean I can sit on toilet forever and just wait and i all get a couple of drips but that's it its not painful its more irritating because I can feel I have to pee and it's bothering me also sometimes after I pee I'll get like a cramp like after I pee all I can it like a muscle or something in my bladder like squeeze s tightly for like 15 sec n then it stops that use to happen a lot when I peed but not as much anymore just really why do I feel like I have to pee but I can't ?