Got back into Blockland again.
Sorry in advance, I'm pretty bad at explaining things like this.
Found out when I use my mouse it will frequently change directions and move at a steady speed in that direction.
Like if I'm trying to look left and move my hand to the keyboard, the reticle will change directions (usually down) and continue in that direction till I flick the mouse.
It's so frequent that I've been having to play with my laptop mouse pad.
Any ideas? I'll probably try reinstalling the mouse software now.