Thank you Elyse, for the information,
There can be a few possibilities for the headache.
Tension headaches can occur on both sides of head.
Migraine headaches can also occur there but it is usually on one side.
When it is predominantly on right side it is a possibility.
Temporal arteritis, cluster headaches, aneurysm, bleed, tumors are other possibilities.
When it starts in the neck, there can be a possibility of nerve impingement too.
As you are not feeling any improvement with so many medicines, I would suggest to take an evaluation by a neurologist.
Repeat scan & other blood tests can be considered.
Till then please continue the prescribed medicines.
Try to relax & avoid stress.
Please avoid caffeine, if you take any.
I hope this information helps.
I will be happy to assist, if you need any clarification.
Please feel free for any follow up query.