I have to agree with DDV's response but add a little to that...
I have found myself in your situation many times, and for the most part I sometimes fall back to the ackward feeling of insecurity and self-consciousness. The best recommendation that I can make is to study yourself when you are self-concious and then another mindset that you prefer. Take the time to compare both. Notice your body language, your energy levels, what it is that you think about, what your breathing pattern is like, etc. Eventually, you can start modifying little things about yourself when you feel uncomfortable and bring yourself to a more agreeable state of mind. It's kind of like physical triggers for your mind.
For example, when I loose my confidence I tend to slouch and speak in a softer tone of voice. I found it that standing/sitting up straight and speaking louder reasert my confidence and helps triggers my mind to change to a more confident state.
But thats just roughly what takes place for me, you have to take the time to make it work for you and figure it out. There is really no one way to fix this, but these are some clues to help you figure out your own situation. It's still a work-in-progress for me and i've been working on this part of myself for quite a while.
I hope this helps...