Saggy boobs at young age

I’m only 19 but my boobs have shrunk recently and became saggy and deflated kinda flat and it makes me very insecure. My boobs weren’t extremely big, I used to wear 32C but now they’re like a B but just so deflated looking and unattractive to me. I’m also worried because I’m so young I don’t know what I did to make them sag so easily.

Does anyone have recommendations on things I can do or use to help them grow/become more firm/less saggy/prevent further sagging?

TIA!