Being surrounded by people who are looking at people is a normal part of modern life. You don't mention your age (I presume you are female) but if you are in your early 20s (late teens for men) onset of schizophrenia is a possibility. If you are using recreational drugs they are even more likely to produce this level of paranoia. As we said in the sixties, "kick it 'fore it kicks you."
If you are late teens and female, or are late 20s or older, schizophrenia is a lesser concern. You don't write like a schizophrenic, and your observations are mostly within the range of subclinical paranoia... anybody could misinterpret random activity around them as being personal. I think that is what you are experiencing, and if cocaine, meth, or ecstasy is involved I would bet on it.
EDIT - for those who wonder what I mean about "writing like a schizophrenic", here is an example:
https://answers.yahoo.com/question/index?qid=20131220143404AA7vR7Q
參考: Mother was schizophrenic (like 1.1% of adults)