when i press one of the move buttons it sometimes takes it as i tried to break/create a block

When I try to walk/run/fly in my worlds, and use the move buttons, it sometimes starts moving screen (my head) or breaking blocks. Also when I run (for example run away from monsters), it starts moving screen instead of running (it stops running). In creative it breaks blocks and places another on where the broken block was, and makes building quite hard. I'm not sure if it's because the settings I have or just a bug.