I don't know about the "act confident even if you don't feel like it part". Faking confidence raises stress for me. Shouldn't I be honest if I wasn't confident? Or work around it with humour?

Think of confidence as a perspective rather than a defined state. Everyone will have their own view on confidence and even though it will be similar to somebody else's, it is experiential. Instead of worrying about "faking confidence", try thinking about what confidence means to you. Ask yourself how a confident person should act and feel and how does it differ from your own actions and feelings. Maybe you could look at someone who you believe to be confident and see how confidence manifests itself. Focus on what being confident should achieve for you and ask yourself if you can achieve it through actions rather than through a subjective state.