I know the feeling. Initially I used to imagine myself being 16 or 17, but later I decided that 13/14 was a perfect age; just on the cusp of womanhood but still a child at heart. The best clothes for a 13/14 year old are an old-fashioned gymslip and navy knickers, bobby socks and court shoes, with a white blouse and school tie. Hair must be neatly tied back and no trace of make-up (perhaps a smidgin of lipstick). Shirts can be short and bare legs are fine. Tops should be light and short sleeved. Young limbs should be admired!
Any chance of a photo of you in your clothes? My email is <oliver1955@opermail.com> and I have experience in playing young girls. It would be easy to apply to you what I have learnt. You would learn to act like a real 13/14 year old girl, and I would set you classwork and monitor your progress. Of course I would punish you, but only when necessary, and in a way I felt suitable for your tender years.
Please contact me if you are interested.
Oliver;)