Well, it depends. If you are not innate, your should considerate postnatural. The mainly reason is the muscle of eyelid and eyeball. Generally speaking, the bulge degree between right and left eyeball within 2mm is normal. If not is abnormal. Then you'd better see the doctor. If you are nearsighted, you can combine frame glasses with contact lens.
I'm pretty sure you are completely normal. Just be thankful that you have two healthy eyes. I don't think there is any way that would change your eye shape. You would probably be wasting your money. Learn to love yourself the way that you are.
By the way, one eye can also look larger than the other if the eyelid is higher or lower.
If you are very concerned about it, then go see the doctors. It also possible that it may caused by disease.
Well, I am so sorry to hear that both of your eyes are a little bit different in size, which might make you appear to be strange. As a matter of fact, one of my friends have the same problem and it is quite weird. However, if you really get upset about this, you might want to get a plastic surgery if necessary. The reason, I believe, is inborn defect. So, take it easy and try to apply some makeups to help you.