I've been having the same problem with one pupil for several weeks, and both a neuro-ophthalmologist and neurologist believe I've been having migraines for a long time. Sometimes my pupil is large but the headache is nonexistent or not too severe, and they think those might be "migraine equivalents." The first step in my case is to stop the use of all over-the-counter pain medicine, as apparently I'm having rebound headaches from regular use. So I think you might consider seeing a neurologist who specializes in migraines.
A related discussion,
larger pupil than the other was started.
A related discussion,
Pupils in the eye was started.
I suffer from something similar. I have a Generalized Anxiety Disorder so I am on medication. But I noticed that my right pupil is larger than my left, and began getting headaches. At first I thought it was the medications but the headaches continued. So, I went to the doctor yesterday and he said that a tumor or aneurysm were ruled out and there was no sigh of neurologic disorder. He recommended having an eye exam. The headaches vary sometimes they are mild but yesterday evening I had a good one. I notice bright lights, driving at night and computer/television aggrivates the headaches. Do you suffer from the same? If so, I would go to your eye doctor too.
Hope for the best, and Merry Christmas.
check out adie's syndrome. A benign condition affectiing nerves in the eye.
There are many things that cause your condition. If it is in conjunction with a headache, I would seek the advice of a GP and get a referral to maybe see a neurologist or an ophthalmologist. You should never try and self-diagnose your problems. In the meantime, dont worry too much about it, it could be nothing at all.
This site is good for answers to questions on how to approach doctors, but not to get a diagnosis. Definitely seek medical advice from your GP on what steps need to be taken or if your condition requires further evaluation at all.