Clicking the mouse stops the player from moving

Every time I click the mouse my player stops all movement, putting me in risk while attacking mobs, and slowing me down all together. It isn't mining that stops the movement, because I tried to see what the problem was, so I changed the mining and hitting commands to one of the keys on the keyboard, and I could me perfectly. I would keep using it this way but it is hard to move and mine with the way I changed it. To make it clear, once I click the mouse, I stop movement, and then I have to tap the movement keys again to move.