Look up Aniscoria. If you were not born with the pupil size difference you may want to get a neurological exam.
Best wishes.
Pupil size is more than likely genetic. Which other family members have the same condition.
How long do you spend in front of a computer screen? Do you use florescent lighting? [Unlike incandescent, florescent lights 'flicker' at such a fast tempo that only your brain and eyes can tell and react to it. In some people, it causes eye aches and headaches and eye muscle aches.]
Get away from the computer and spend time outside using your distance vision instead of inside using close up vision.
If after a few weeks things don't improve ... make an appointment with an eye doctor ... an Ophthalmologist ... not an optometrist ... good luck.
Thank you for all the comments.
There are no other family members with different pupil sizes. I don't spend allot of time in front of the computer, i do however spend allot of time painting,sculpting and drawing in my studio which has florescent lighting. Maybe that is the cause.
Thanks for the help!