I was almost caught being an atheist

[Succubus]

Today I watched a video made by the atheist youtuber Holly Koolaid in my room and dad entered and saw me. Luckily he didn't get what the video is about and I invented another explanation which he believed. He got out of my room so I got on this forum. A few minutes later he entered again and almost caught me. I tought about locking up my room so this would not happen again, but I tried it years ago and he didn't like it. He's obsessed with controll. What can I do to be sure that I wouldn't get caught? I don't want to risk by telling him I'm atheist untill I'm financially stable.

Even sharing a house as an adult, my mom hated locked doors. I hate to say this, but he owns the house or pays the rent,  And especially if you are a kid, he's going to see it as  his to control, that is just the way parents think. My advice is only do this outside the house, or wait until you get your own place and then you won't have to worry about what he sees or thinks. 

Seems you already gave yourself the answer in your own post. I've never been a fan of authoritarian views, but adults do see their kids as being told what to do more often than not. It would be nice if communication and cooperation were a common thing taught to society, but when it comes to kids, most of the time the parent sees themselves as the dictator. Fair? Not always no, but it really is how most parents get raised themselves.

I loved my mom, but we made lousy roommates precisely because she always thought that it was her role to tell me what to do. She always loved me and I always loved her, but I felt much better when I was out on my own.

This is wrong on so many levels. She is not a kid she's an eighteen year old woman and as such she has a right to privacy. Your mom hated locked doors? Well that was your moms problem not yours. What's good for the goose isn't necessarily good for the gander. There is something very unwholesome about an adult, unannounced, walking into a woman’s room. It just is not done, not in polite society anyway.
But then in my view this latest revelation from Die Atheistin is placing some strain on the credibility of her saga.

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Don't wear headphones and put your speakers on mute. Do reading instead of watching videos. Or watch videos on mute . . . if you don't need the sound.

That way you can more easily hear when daddy is coming.

'I' got it. Kudos.