One eye being "larger" than another may either be a problem with eyelids or with the eyeball itself. If one eyelid is retracted more than another, or conversely more droopy than the other, the size of the eyes visible will naturally be different.
The position of the eye within the eye socket [orbit] can also affect the size of the eye. In thyroid eye disease, the eye can become more bulgy as the muscles/fat behind the eye may become enlarged. Complicating the issue further is a change in eyelid position [retraction] which can make the appearance even more obvious.
Rarely tumors behind the eye [usually benign] can push the eye forward making it seem larger. As mentioned previously an evaluation by an Oculoplastics/Orbital surgeon is necessary, sooner rather than later.
The appearance of one eye bigger than the other can be due to changes in the bone or soft tissue around the eye or the orbit or sinuses. It would be important to look at old photographs and for you to be evaluated by an experienced orbital surgeon as many of these condition can affect your overall health. The good news is that once the cause is identified there is specialized surgery that can improve the appearance and symmetry. Again an experienced orbital surgeon would be best to evaluate and treat the process since this is a very delicate surgery.
If one eye is bigger than the other, filler or surgery may be options
If one eye is bigger than the other, depending on the situation, either manipulating the eyelid or the eye itself with surgery or filler can make the eyes look more symmetrical.
Eyelid Assymetry Needs to be Evaluated
Without a photograph or more extensive history it is hard to answer your question. In most cases, assymetric eyes can be made to be more symmetrical.
If one eye is becoming bigger, it needs to be urgently evaluated by an Oculoplastic Surgeon. Very often, this is a sign of thyroid eye disease. Another cause of an eyelid becoming bigger is a growth or inflamation behind the eye. Sometimes, the larger eye is actually normal and it seems bigger beause the other eye is becoming smaller.
The bottom line is to see your eye specialist and discuss the appropriated course at that time.