Multiresolution subdivisions are creating curves down the middle of my model I am currently doing some character modeling and I decided to add a multiresolution modifier to my model. However, when I add subdivisions to my model I get a bunch of curves down the middle of it. My model does not have any of these curves without the subdivisions from the multiresolution modifier.  Can someone please instruct me on how to fix this?
Looks like you have internal faces down the middle (probably left over from a mirror modifier). Delete all the faces that are inside of your guy, they are on the center, right where the crease is. 

You can easily remove any interior faces. 


Tab into edit mode, make sure no part of your mesh is selected.
From the 3D view header Select > Interior Faces.
Switch to wireframe with Z and if you have any faces selected press X > Faces.