I am a funny, and good guy, but I am really self-conscious around people, Why?

...My girlfriend says "I have so much potential to be outgoing and friendly, but I am so self-conscious around anyone." I am not really being myself around different people, I feel so quiet all the time, I feel so alone, no one to trust other than her. I even feel I cling to her. She deserves so much better than me because she loves meeting new people, I dont. I feel like I am letting her down because of my inner problem. Maybe its anxiety? Anyways I used to be on prozac because of this problem but then I quit because I thought I could overcome it again. After 10 months, I feel low again and I have troubles concentrating on everything. Its hard for me to get out from bed, and sometimes even go to bed! I think I am going crazy. I am just tired of everything, especially dealing with people. I wish it was just me and my girlfriend living together. I feel hoepless because I want to "get out of my shell" but its just so hard to do things thats may sound simple to "regular" people for example hold a conversation. I can only be good at communicating with other people when I drink alcohol, but I dont want to depend on it. I already seen a psychologist and that didnt work, I even asked her if I can go back to prozac, but I want more opinions. It is really hard for me to go out without drinking coffee or alcohol, I just dont care when Im around people, like I avoid them because everyone expects confidence, everythings good, etc. If anyone has time to read this and help me with a solution. Thanks :). How do I help myself overcome this lack of interest of people,friends, especially talking?