I have been told many times that im really pretty but im shy so..?

yeah so i dont talk much to people unless i know and feel comfortable with them.it has been mistaken as cold/unfriendly and stuck-up cuz whenever guys talk or flirt with me, i dont really ..do anything. so i heard this guy said that " she thinks she's too good to talk to anyone" it's NOT true. how can i overcome my shyness?