Bug rotation mouse

Hi I’m french but i hope you’ll understand me.
Well. I’ve began a collision detection in a 3D world, and with a 1st person camera. The view point is controlled as lot of FPS, keyboard for movements, and mouse for view rotation. But i have a bug : when i bring my mouse up (the most top), i cant turn left or right. Same when i move my mouse down. The viwe is bloqued.
Here, i hope you’have understood and thanks for your help !

Post some code if you want some help because it’s really hard to say what is wrong.