I sustained a head injury back in November when I hit the top of my forehead very hard. I was experiencing a very deep headache, constant sinus pain, sharp pain behind eye, facial pain in cheek, ear ache, toothache, light and noise sensitivity, tinnitus and hypercusis. I also experienced fatigue and insomnia. The pain was a dull throbbing sensation. Are these typical symptoms of TN?

My symptoms have improved greatly with 60mg Cymbalta backed up with Imigran. Now I have a dull headache which worsens with too much activity, but earache, tooth ache and ear ache doesn't go away when it comes. When the headache worsens it is like a migraine with other features of facial pain, it goes away though with the combination of Cymbalta and Imigran.

From what i know about Trigeminal Neuralgia, having had it for over 6 months now.. is that the pain varies from person to person. Typically it is felt on one side of the face (usually the right) and is an electric shock/ shooting type pain which is very painful. The pain lasts for around 30 seconds. You can get regular attacks or infrequent attacks.
I believe there are two types of TN though.. the other being the more constant pain which you described.
I was diagnosed by a specialist at hospital after i initially responded well to a drug called carbamazapine. This is usually how they determine whether you have TN. There are other anti seizure drugs they can try you out on to see if it helps with the pain and if it does.. it can usually indicate that you have TN.
Also.. if it is the most painful thing you have experienced (9 OR 10 on the pain scale).. then that is also another good indication that it is TN.

Have you had an MRI?

I doubt you have TRI geminal as you would normally have sever pain on one side of your face, not your head. And its not caused by concusion, but by removal of the melanon sheath near the base (usually)of your brain, not your forehead.

It sounds like this is all guesswork. You need imaging and a doctor to help you.