oh no....your head model, the geometry is really bad. How did you get it like that? It seems like you used some kind of simulation or something. I know when you use cloth simulation, you get that type of geometry. If you were to ever plan to rig this head, it wouldnt work at all. Not only can you not rig it, it's almost impossible to add details to it with modeling. If you create edge loops, you'll be able to add more geometry that will follow the anatomy of the head. Your current mesh right now would make a bunch of unwanted pinches and wrinkles. :-p

Try to get your geometry to look like this pic ref I've attached.
let me know how it goes, if you need help you can talk to me on my AIM which is Andy95121. I'm not that good yet, but i can probably help you get started in the right direction.