If you haven't noticed any other concrete paranormal activity and you say you don't think you have experienced a personality change then I think we should table the demonic angle and try to rule out all other possibilities. Also can you think of a reason something paranormal might have marked you like have you been to any known haunted places or come in contact with any new people that you got a weird feeling from, If you haven't noticed any activity and these scratches were very recent we can assume that whatever triggered them are relatively new. Keep note of when things happen and try your best to debunk them, and to answer your question to the best of my ability demons attack when you are at your most vulnerable. I don't know why you didn't wake up but my friend got scratches on his neck that look very similar to those and he didn't notice for a couple hours until his neck started to burn and one of our friends saw them.