How to be confident all the time?

Sometimes Im Confident and sometimes im not. Ok so lately I have realized that I am a confident ,funny, interesting guy when I am around at least two of my friends. Like if we are at a place where there are 50 people and I have like two friends there I can be outgoing and funny and make a lot of new friends. Now lets take the same situation when I am by myself I just clam up. I only speak when im spoken too. Any Advice.