Thanks for the support Demunie.
My dad found out a few days ago actually, via email - I sent him a long detailed email describing my emotions, depression, self harm and everything, but my brother saw the cuts and told him - I don't think he knew how bad they were, so he was okay with it until he started freaking out.
He told my mum about the cuts through the phone (they're divorced) and she thinks it's a phase like my dad does. She joked around with it a bit though - but she still just tells me "you should probably stop that".
I also spoke about seeing a psychologist in the email, my dad said he'd talk to my school but he hasn't. I'm going to bring the topic up again in a bit.
(Also I think I already posted a reply - not sure though. I'm new to this website, so... excuse me if I post twice. )