Any work of art is automatically subject to copyright - you do not need to register, or make any payment. If you made the drawing on your own behalf then you own the copyright. If you were commissioned to make the drawing then it is likely that copyright belongs to the person/organisation that asked you to do it. With a piece of writing or something similar a good way to prove your claim to copyright is to mail yourself a copy and leave it unopened - the postmark proves the date. With a drawing you could possibly make a copy and do the same thing.