Stavios you competed in a good show.
At the big shows, such as the nationals here in the USA, everyone is pretty darn good, so the difference between a first and fifth place physique is not that major. Placings are subjective and can go either way.
I hear you as far as being frustrated with the outcome. I compete to win myself.
I can honestly say, you worked your ass off, dieted hard, and didnt bitch about either one. And were in the best condition of your life so far
You have no control over placings.. I have been to many shows and have seen all kinds of lets say "unusual" placings, dont get too down on yourself. ( easier said than done) but hey bro, im not calling it from the sidelines, i compete in the sport and know first hand
You were in great shape, you just need to fill out more for your height, you know that It takes some time, and you will work on that.. have some good food, spend some time with your girl, your family etc.
I know your passion, once you really think about this, your going to train heavier, stay tighter off season and work on filling out your teenage body.. Bro this was not your best.. It was your best look to date, way far from your best. Your best is yet to come
you have many years ahead. Use this experience to motivate you to be better..