I am having severe pain in my head, eye pain and in my ear and externally behind my ear down my neck all on the left side. what could it be?

Focal headache: You should really be seen and examined, as there is no way to tell apart a long list of possibilities. Here are only a few: migraine, ear infection, TMJ, sinusitis, tonsil infection, dental infection, arteritis, cranial pressure, vascular problem, neuralgia, etc. Basically almost anything. "Severe and focal" means you need an exam ASAP.