I can relate to this. I too had similar issues when talking to unknown girls. But was able to talk to girls whome I knew. I still have problems with eye contact but working on it... I will share my experience... Lack of confidence in me was due to fact that I was thinking what that girl would think about me. I realized that if you think good about you, you are confident, if you not doing anything wrong, why should you care what she thinks about you. You should care about only what your loved one will think. Remaining everyone just don't give a damn. The day you realize this properly, you will become more confident from within.