Crease Too Low After Double Eyelid Surgery and Slight Imbalance, How Can I Fix This?

It sounds like you had a suture type of eyelid surgery. This technique frequently is characterized by quick recovery but also small folds. You may need to consider an incision surgery if the crease ends up too small. 

If the original surgery was an incision, then after 6mo of full healing, you may either undergo some skin removal or a second incision made above the original incision.

It is much easier to fix a fold that is too low and very difficult to fix a fold that is too high.  Three weeks after surgery is a very brief time frame.  You need more time to heal.  These differences might resolve or get worse over time.  At 4 months after surgery, you will be in a place to decide if you like the result of this surgery.  At this point if things are not better you can begin to think about with your surgery if something more should be done.

There is usually some swelling immediately after surgery on your upper eyelids which would make them look more swollen and wider than they will eventually look.  If they appear too low to you immediately following surgery, they will tend to look lower and the crease will be closer to the eyelid margin as the swelling goes down.  It is possible after complete healing to revise your eyelids so that the crease will be higher and stay higher.