Is it necessary to register copyright of a song written & composed by me?

I would like to know if I need to copyright my song which is written and composed by myself. I have email exchanges related to distributing the song to music arranger and have uploaded the song from my youtube & other platforms for distribution. Will it not be enough as a proof of my copyright? I am a small time musician and does not have much resources to get into legal formalities. Please do let me know.