Confidence is something that comes from you, nobody can give you that. It's all about getting into the right mental state, and you can apply that to everything.
here you have a video of the things that I use to go out sarging. I know this is not your case but the idea is the same, sometimes you can use external factors to boost your confidence. Hope you understand what I mean.
http://www.youtube.com/watch?v=V-WCQTlH ... XvDO5SHQKM
But never forget something, she's with you. She could have dated all these other guys but she's WITH YOU. Don't project your insecurities