I am very shy and come across to people as stuck up how can I learn to be more friendly!?

I am 18 yrs old and I am very shy on top of having anxiety when being around people. When I walk up to people or try to have a conversation I feel like I instantly make them uncomfortable because I am so quiet and its obvious I am uncomfortable in the situation too. Some people can tell that it is just because I am shy and I am actually a very nice person but others see me as bitchy. There have been times were people have thought that I didnt like them or i was irritated because I look uncomfortable or dont talk much. My boyfriend told me that his mom thinks I come off sorta bitchy which really hurt my feelings a lot. People who know me well know that I am not a bitchy stuck up person at all. I want so badly to be more bubbly and friendly because I really am I nice person and I hate that I come across this way.