Help with confidence

I'm a really shy person. I'm 22 and still deal with my shyness and anxiety from being abused as a kid. I'm in college and I have a presentation for a course this week and I'm really nervous. I've been having a particularly hard time lately being confident despite other people pushing me down. Today in class a guy laughed out loud at me when the professor called on me. I HATE to let this bull shit get to me but I can't deny that it does. I'm 22!!! I want to be over this!!!! How can I let this go and be confident in me and get over this anxiety?