Sometimes Before I Pee I Can Feel A Burning Sensation.

Sometimes before I pee I can feel a burning sensation. Most of the time after I pee I feel a burning sensation and stabbing pain for an hour. It helps me to sit down. I want to be alone during this pain and being in school when this happens is horrible. Most of the time its worse durning my period but now it's happening every few days. When I pee I'm fine but the afterwards is bad.