PAIN only on one side of head could be due to trigeminal neuralgia(such pain is electric shock
like and doesnt go behind the ears or down in the neck) your pain is dull ache so it can be ruled out.....but if you have irritation or pain in other parts of body too then it could be generalised weakness either due to electrolyte imbalance
or due to some depression
....if you do not have some depression or other medical illness ,get your ears checked .
if ears are normal take multivitamins and healthy nutritious diet and take a break from busy schedule.