Yes i am the same i am super nice to everyone and it is only really my family that sees my mood swings. I think it is mostly because i am so scared that if anyone saw me like that they would NEVER speak to me again and would leave me i also feel like if i am nice people would be less likely to leave but i am not really that nice i just act nice cause i am desperate. I also internalise things A LOT and i am always punishing myself.