Oh yes... Feel free to use first person. On one condition: State the name of your character in every post. You could simply use center tags and type it in at the top of the post. I ask this because other people need to be able to refer to your character by their name, and if there's nothing but "I" and "myself" they might have trouble with this.
Just understand that some people superficially dislike first person and that it may effect the way people read your posts. Good writing should compensate for this, though.