If you haven’t seen the FaceBuilder Addon yet, its worth it playing with it. With just a few pictures of your own head, you can easily get a model of your head in Blender. The pictures need to be the same resolution and field of view but you don’t need to know the specs.
It’s been a while ago I tried out this addon, but it would suffice if I tell you the big lines. There is already a head-model in the scene when you start de FaceBuilder addon. What you do here, is lining up points with your Pictures. Start for example with the point of your nose. Then things like: chin, corner of your eye, ear.
Then you go to your next picture and line up same or similar features of your head. Lining up points is getting easier during the progress because the model of the head lines up more and more.
You can download the facebuilder addon on https://www.keentools.io/facebuilder Look for the tab Blender. The Blender version is “Free open beta”.