You need to go see an ophthalmologist righ away. multiple potential causes but if it has remained that long, you need to be checked very carefully. Depends what your age is. Find one at www.aao.org. Do not delay.
HV
I hope you have seen a neurologist for this and have also had CT scan and MRI/A of your brain as sometimes there are other causes of increased intracranial pressure (brain tumor, sinus thrombosis etc). You may also try loosing weight as that relieves intracranial pressure as well through poorly understood mechanisms. Good luck.
HV
i had the same complaint but it is recurrent and lasts for short time then goes out , recently this condition is repested more frequently ,fundus examination shows aedema of my optic disks (papilledema ) . iwas adviced to take cedamex tablets to lower the intracranial pressure .i'm taking the tablets for a shot time but besause of it's side effects i stopped it