I found a wonderful website which has lots of very comprehensive information on how to pass. The page finishes with this bit of advice, which I found very comforting:

Finally, a very large part of passing is sheer confidence and bravado. If you really believe you’re a man (which you are) and project this belief to the rest of the world, it will go a long way towards also convincing others. Any difficult feature you might have (high voice, smooth face, small shoulders, wide hips, lack of height, etc.) is one that some non-trans men have also – there are even non-trans men with enlarged chests (male gynecomastia).

My biggest issue now I have my binder is my voice. My face is very smooth, and femme, but I have learned that combined with a deeper voice, I am immediately taken for a teenage boy, rather than a woman.

The last three days my voice seems to have been higher than usual. I have felt extremely demoralised by this development. I have a cold that at first made my voice much deeper than it usually is. That was great, I was passing left right and centre. The woman in the Bakery thought I was a teen going through the horror of a breaking voice. I loved it. Now though, I seem to have a bit of goo clogging my voicebox so I just can’t speak in a lower voice.

Its driving me nuts. I think that I need to practice speaking in a deeper and more monotone voice.