Can a lot of excessive time being in front of a tv screen cause droopy eyelids? if yes, can it be treated in some way? i'm only 20 years old.

No: There is no functional difference between tv viewing and video screen viewing such as on a computer. If there were a relationship causing droopy eyelids, we would be in the middle of an epidemic. You are young to have the older age eyelid type of drooping, so best to get a quick check with your ophthalmologist to determine why this has occurred and to recommend remedies.