Being bullied in school has affected my relationship :/

Ok Glow sisters ,

Growing up I was constantly bullied by my peers from middle school on up. I was called ugly , stinky, people would pull my hair and pass around awful notes about me . Every time I came in contact with another human being they would betray me and talk behind my back. So after graduating high school I always isolated myself and never went to any partys ,clubs or even family dinners afraid of what people would think about me . I met my wonderful boyfriend of 3 years in 2013. And I have still not been to any of his family dinners (thanksgiving, Christmas, etc) , sometimes he begs me to go to clubs with him and other friends but I always turn it down because I'm super afraid to interact with people because of my past. Today was his grandmother's birthday and he asked me to stay for his family party. I bit my lip and shook my head no. He had a look of disappointment on his face and explained to my how I had hurt his feelings about not wanting to be around him, his kids and family. But I want him to understand its not him. Being 21 I have tried to grow out of it but I still find myself being nervous around large amounts of people. My man wants to take it to the next level with me but I can't seem to out grow my past . Ladies please help.