I need to build my confidence and ability to cope with critical people, pls help??

I am an introvert. I have always been shy and quiet basically. i am friendly, smilley, probably too much so actually. My problems are that no matter where I work I encounter problems with covert bullying. I never have problems with guys and treat everybody well. i am sensitive, hence why I work in my job, but I can pick up other facial expressions and body language, voice tones etc and if they are negative toward me, I just shut down more. I worked as a bridal model whilst at Uni and people tell me that I get picked on for being pretty, tall and educated along with being too eager to please. How can I make myself care less about other peoples negativity toward me??