How to fix duplication of materials with blender?

I’m wondering how to fix a level I’m exporting from Blender to Unity. The problem is that my Blender model has a total of 37 materials, some of which are not even being used in the mesh yet, but the exported fbx model shows 52 material slots in the Unity mesh renderer. For some reason, every time I unwrap something in Blender, it adds a new material slot that’s visible in the Unity mesh renderer. Does anyone know how to combine meshes with same materials in blender? My mesh is very low poly, but performs horribly because there are so many duplicate material slots in the mesh renderer.

Nevermind. I already figured it out. I had to make sure the material texture matched that which was shown in the uv editor.