Why is one of my eyelids getting progressively 'puffier' than the other? (Photo)

you need to see an oculo-facial plastic surgeon to evaluate you completely. it appears that you could have left upper eyelid ptosis and possibly proptosis of the left eye. Please, don't think this is your diagnoses. From picture it is hard to diagnose anything. But from the picture it appears that you need to see an specialist. 

Thank you for posting your case.  You should see an oculoplastic surgeon as soon as possible.  There are many different reasons why you may have this condition and often a CT or MRI scan is necessary to determine the cause of the problem.  There are many good ones in the Baltimore/DC area.  Good luck!

Since this is a new issue, you should certainly have an in-person evaluation with an oculoplastic surgeon (there are many excellent ones in the Baltimore/DC area). It is difficult to tell from the photo the exact nature of the problem, but it likely warrants a full consultation and possible additional testing with imaging of the eye socket.