Unfortunately that's very situational and I can't answer that, haha. The best you could try to do is to step back and take an objective look at what happened, preferably some time after the incident if it made you feel emotional (angry, sad, worried etc). If what you meant by your previous post as being -> I've had unpleasant encounters with a certain group of people, I now overthink about different people in the same group then I'd probably say it's overthinking, but once again it really depends how small the group is, how bad your experience with them was etc. Also, overthinking is a natural thing and so is being anxious, I'm pretty sure for it to be paranoia it would have to fall into the unreasonable category, something which I'm sure anyone you tell your story to would be able to discern. I guess I would start to get worried about it if the worry got so bad that it prevented me from doing something normal, if it lasted for a long time without getting bad. Surely paranoid people would not believe they are (possibly) paranoid, haha. Also, by doctors did you mean would doctors diagnose you with it or that the event was in relation to a doctor, in which case it's much more serious