I think I worked out what happened with the shading. I just tilted my laptop screen slightly further back than usual and wow it was bright so I think the brightness of it depends on what angle people have their screens at and general screen brightness settings, from now on I will be more careful how my screen is.
I've done it before where I thought I colouring something really brightly or really dark and I moved the screen forward and it looked really pale so I had to start again :p It's the one thing that annoys me with digital art.

Also, thanks~!