I can relate too, I'm the same, I have a husband and family who I socialise with with little or no problems and I can get on fine with easy going, good natured people, but put me in a situation with people I don't know very well, who are gossipy, judgemental and generally think a lot of themselves and I find it so incredibly hard to relax. I think it's because I want these people to like me and think of me as equal to them, but deep down I feel I'm not likeable or equal to them - I know that it really shouldn't matter whether these people like me or not, and I'm sure that even the most confident people come across others that don't like them, they just don't let it bother them too much. Whereas for me if I get the impression something thinks badly of me it a bludgeons my fragile ego into pieces.
To be honest with you I got worse when I got pregnant, I had a difficult preganancy and was unable to go out a lot due to severe sickness, when baby was born I was so happy and I didn't care about anyone other than my baby and hubby for a while, but eventually I found myself feeling even more insecure, because I started worrying about protecting my baby from all the horrible people 'out there'. Also because I gave up work I had no schedule, no reason to go outside and meet people and it was too easy to just stay at home with baby. The reason I tell you this is so that you can be aware of it and try and head it off before it happens.
As by daughter grew up and started to need social interaction I sort of transfered my anxiety onto her, I'd get really upset when other children were mean to my daughter and felt I should protect her from that - which is totally the wrong thing to do - I realised that unless I let her get used to the fact that people are always going to find fault, be mean, etc., she will end up feeling like I do. What I do now is try to instill enough confidence in her so that she will be able to hold her head high regardless of what others say/do/think, hopefully, she will know inside that she's just as good as everyone else.
There's never going to come a time when everyone I meet is totally into me, doesn't judge me and is never cruel, I either have to learn to accept it and not take it to heart or continue hiding from it.