Dear Blue,
I can totally relate to what you're saying and honestly, I think it is a mild case of paranoia which stems from Anxiety actually, because I used to notice the same things too. I would be at work, and I would get one little look from one person, and I would think to myself, "Ok, what are they thinking about me now?" Or if there was something funny between a group of people, I would think sometimes that they're actually laughing at me for some reason.
To some people, it may seem like that song, "You're so vain"....haha, but that's really not it at all....the other way around in fact...insecurity, which is another issue this mild paranoia may stem from. I still get it most days, but just try to brush it off my shoulder and pretend that it's all in my head, but I'm not so sure it helps completely, or maybe I just bottle it up inside....either way, not good I'm sure!
In conclusion, I have talked to my therapist and he thinks I probably do have a mild case of paranoia, and sometimes I think it's more than just mild, but it's yet to be taken care of, so I dunno exactly what to tell you, except try not to notice things so much as you usually do, concentrate on yourself, and not what others are doing....seems to work for me sometimes. I wish you the best of luck in finding a solution.