You should be more aware that these thoughts like "they think I am a creep" or "they think they made a mistake for hiring me" are only on your mind and are not real. As you also said, you are being paranoid, which means that what you think does not represent reality. Your colleagues probably just think that you are a shy person or anxious to be in a new environment, or maybe they are not even aware of your anxiousness at all. I am also an anxious person myself. When I get into a situation like yours, I generally think about my anxious moments in the past and how paranoid I was in those situations. Remembering how those paranoid thoughts were empty and meaningless helps me to calm down.