I have always felt like that too Freya.

I always used to decline invitations for social things, be it a school thing or something else out of fear I woudln't fit in or they would one day find out 'what I was really like' and wouldn't want me around. One day I decided to say YES to invitations for a whole month and it was amazing. I found I did fit in with everyone and they actually DID want me around, the more I said yes, the more I was invited and then I started inviting them to things and they'd come! I soon found that I had amazing friends, we've all drifted apart now that our kids have grown up and gone to high school but still get together on occasion.

I think the only way out of it is to step out of your comfort zone. Do all the things you fear doing and soon it will all become easier.