Joanna, you obviously have some weakness of the muscles that lift your lid, or some stretching...or perhaps scarring....of the ligaments that lift the lid. The drooping of the eyelid, no matter what the cause, is called "ptosis." If/when it bothers you too much, an oculoplastic surgeon can fix it.

Here's something that is interesting that you can try. I would like to know if it has any effect for you, though your problem is not constant like mine: I accidentally discovered that Visine LR eyedrops will temporarily stimulate the nerve that activates the lifting muscles of the lid, and for 6-7 hours, my eye will be normal. It is a great comfort. The downside is that after several days of using the drops, I develop rebound, just like using Afrin nasal spray, since the chemical is the same. My eye is worse when I wake up, and I sometimes develop an annoying nasal stuffiness, since the eye ducts and the nose are closely connected. But if I want to look normal and see normally, I can use the drops.