Do I have pseudo "Double Eyelids"? (Photo)

I used to have monolids but a crease started forming on my eyelids when I was 12. The crease would appear and disappear but eventually stayed there permanently. It's uncomfortable and I can feel my eyelids fold when I blink. However, when I look down, the crease disappears. So I was wondering if it's not actually a double eyelid but just extra skin that folds over when I look ahead.