You need to see your GP without delay and be examined, as it has come on fairly quickly.
There are many causes for this, and examination and or tests are needed to get a diagnosis.
Maydup its the refrence to it causing sleepyness that is worrying, fatigue would not cause that. tamborine if you can't get a GP this morning go to A&E !
I agree with sqad that there are many causes for this, and one of the most likely is muscle weakness due to age. However this usually comes on gradually.
I also agree that a stroke is not the most likely cause. But it cannot be excluded without taking a full history and examination. It certainly cannot be excluded over the internet.
The advice for sudden onset of a drooping eyelid is that one should seek medical advice promptly.