I'm scared that my dad will hit me?!?

[Alexandra]

Okay well today has been a really busy day. My mum found out that my dad has been cheating on her for 6 months now and they're fighting now. My dad blocked all of us on facebook so that we wont be nosey on his timeline when a few minutes ago or so, a message from my dad comes and it said that "cris" (the girl who dad has been having an affair with) is asking me to tell my dad to call her because she's 'worried' but i refused and showed it to my mum. Now she's angry and upset. She told me swear to her and say whatever my heart says. So i did then my dad calls my mum and asks why am i saying stuff like that. So yeah it's basically like that. Now im scared because what if he comes home and abuses me and my mum?! My mum says to call him and express my feelings but i refuse. Then she says "do u not care for me" im sad she thinks i don't care about her now what can i do?! PLEASE HELP I JUST WANT EVERYTHING TO BE HAPPY AND THE WAY IT WAS BEFORE!! ( im 13 btw