I've been noticing my problem for a couple years but I don't think I was born with this eye size imbalance. This is bothering me though, what should I do?
Learn to love that big eye.
Have you discussed it with your doctor? It looks like Ptosis, read the following page, it might help you talk to your doctor
https://patient.info/doctor/ptosis-and-lid-lag
Good luck
There are many reasons why your eyes can vary in size or appear to do so, it really is though important that you talk to a doctor to rule out any illness if this is something new to you. He/she may referr you to a an Ophthalmologist for further evaluation.