Wow I love your portrait I believe it's fine just the way it is even though its simple. Think of the Mona Lisa it's pretty simple but it's one of the the most famous art work talked about through art history. Self portraits I believe are supposed to be simple because it a reflection of you and only you, so you can see yourself in a different dimension you created. If anything keep that one as your original and pant another maybe this time change what you were, how you smile, the position you want to take. Use it to live out kind of a fantasy of how you see yourself .