Noted.
However, it is more gay having some fat dude spying on yourthrough your selfie cam unknowingly while you are getting dressed/naked.
There is absolutely no way, and I mean zero, someone could be looking at you through your selfie cam without you knowing.
Firstly, when the screen is off, the device cuts the feed to the camera. You can test this by using any number of apps that allow video calling and video call a friend using all of them and turn the screen off during the call. Your friend should report your video feed either freezing or going away entirely.
Secondly, and this is the most important one, the only way someone would be able to have access to your selfie cam is if you installed an app from some unknown source that grants someone access to use your selfie cam without your knowledge. And even then, you'd have to give the app permission to use the camera, first. Apps can't just start using your camera or your microphone without you knowing about it. They need explicit permission, first.
So, if this is a concern for you, go into all the apps in your app manager and turn off the camera permission for every app, except your camera. Or, hell, turn that off also, if you're scared Samsung is spying on you, like someone else on this forum is.
These devices aren't like Windows. You can't accidentally go onto a website and suddenly someone is using your webcam to look at you. Very nearly anything that happens on your device needs your explicit permission. They can't just take control of sensors or install apps willy-nilly without your knowledge.
Also, something someone said once about people sticking tape over their webcam on their laptops; let's say something like this actually happened. Your device is presumably laying on your desk or in your pocket for most of the day. So, for a good portion of the day, whomever is spying through your selfie cam will be looking at a ceiling or a dark pocket. The couple of times that you are using your device, all they'll be looking at is your face, looking at your screen. They can't see what you're doing or looking at, only your face. Why would someone want to hack your device just to look at your face for 5 minutes, a couple of times a day and look at the ceiling the rest of the day (this is assuming also they can access the camera while the device's screen is off, which they can't. So, essentially they'll be looking at a blank camera feed and staring at their monitor all day for that hopeful chance they'll catch you checking your email for 2 minutes, which won't help them anything, again, as all they'll see is your face and not what you're doing).
TL;DR
No need to be so paranoid about anyone spying on you. Trust me, your life isn't that interesting and the ceiling of your work place isn't either.