Is it normal to not know where these scratches came from?

Demons, perhaps

Stretch marks?

I scratch myself in my sleep all the time, I woke up with a deep cut in my arm and I was like "How the heck did that happen?"

Stretch marks, I had the same for a long time, after a growth spurt. After a few months, maybe a year, they began to disappear. They did look like scratches, like from a claw or something.

sometimes I scratch myself in my sleep and dont notice until the next day.

it's common to get scratches from everyday items. A friend of mine even got a slight scratch from a slice of toast lol. Maybe there were some crumbs in your bed or something.

So have you ever seen Aliens?

Were you out in the woods or doing any sort or activity where you could've been scratched and didn't notice? Or you could've done it in your sleep. I get mysterious scratched and bruises a lot cus I just don't notice when they happen