The issue is not personality--rather, the acceptance of the fact that competitive dancing REQUIRES good presentation, and the recognition that your training should focus on this subject as much as movement technique.
Presntation is easy--you just need to acquire the tools and be comfortable with it.
One way to do this is to connect with the audience through eye contact and smiling when appropriate.
Make your dancing look EXCITING rather than looking EXCITED.
About your second concern.
Being short in stature requires a change in strategy in how you put your routines together.
You need to incorporate more spins in the Waltz, for example.
When you find yourself in a forest of tall people, to be seen, you move against the grain (if they're moving forward with Feather/Threes, you Telespin for ex.
That is to say, if they're doing progressions, do rotations and vice versa).
Look for the open floor space to showcase your work (say with line figures for ex.).
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