It could be because of some past experience that you have made a boundary around yourself.
try to gradually trust people, match their words with their actions, it will give you a clarity if the person is trying to hurt or not.
Firstly you need to understand that nobody wants to hurt you. Communication is the key to everything! This is a long process, you gotta talk to people and open up slowly. Start with family and friends and realise that they're all your well wishers. Nobody wants to hurt you in any way whatsoever :)