Why am I always so worried but can't expres it what makes it worse?

PLEASE HEAR ME OUT TILL THE END. Every time my parents or siblings go somewhere, I always start feeling really worried and paranoid just before they come home or if they come late, even if it's five minutes. I always start thinking something really bad happened or that they died or something, which has never happened before. Especially when it's at night. I need to go to bed at ten at normal schooldays and when my dad is out and comes home at eleven I always stay awake for an hour waiting for my dad to come home. And the whole time I feel this uneasy and suffocating feeling and kinda feel sick. And when they come home I feel intensely relieved. But I never tell anyone about this, and they would never expect me to worry so much, it's all because of this: since I was young I kinda created this picture of me being a tough careless girl who doesn't worry about anything, I rarely cry in public and I dont look like an emotional person, I also don't like talking about my feelings, so what's wrong with me and what should I do?