Hi, and welcome to the forum.
First two drawings are not pixel art they are more low res pencil drawings, cause main idea in pixel art is that every pixel is placed carefully and it has it's purpose. Here you just tried to draw, probably in MS paint.
Third one maybe can be classified as pixel art but there are a lot of problems there, you have some redundant colors, edges are not clean, you have some gray outline that doesn't have a purpose etc.
You are probably young, and I don't want to discourage you, but I must say that you first need to learn to draw a bit better, before you try to create pixel art. Pixel art maybe looks like an easy medium but it's not truth.
Practice your drawing skill every day. You don't have to draw on computer, pen and paper will be more than fine. After a while you will see the progress. Good luck.