How to make your nipples constantly erect?

I'm 18 and I have grade 2-3 sagging breast however, when my nipples are erect they look like a grade 1 and look so much better. I also have quite large puffy areolas with flat nipples when they are not erect. I am looking at getting a lift in the future but would rather not have to have scars at this age ( maybe about aged 24).