Skinned Mesh From Blender Doesn't Look Right

SmokeBubble1000

I'm using Blender for the first time and wanted to make a ragdoll. So far everything works except for the mesh. The mesh will deform to match the bones, so the ragdoll part works, but some of the faces of the mesh look transparent and my character looks really weird. I have tried recalculating normals outside and using backface culling on my faces in Blender and it still isn't working. I have also tried using the blend file and exporting the fbx and getting the same results. I'm also using vertex groups. The mesh looks fine if I don't have it as a skinned mesh renderer in Unity.

The left character is without the skinned mesh renderer, and the right one is the one with the messed up skinned mesh renderer.

does anyone know what's wrong with it?