>>1020708
Sometimes when you add new faces, especially with knife tool, your normals get all fucked.

To fix, select your mesh
Mesh > Normals (alt+n) > Reset Vectors

Also your topology is kinda sloppy. You can smooth them out with this.
Vertex > Smooth Vertices
I like to make a shortcut for it, select my vertices, and press it a few times so my quads are more evenly spaced.