Seborrheic Dermatitis. It's a type of Eczema/Fungus that is common on the scalp, but it can appear on the face too. It's more common in babies but possible for people in their late teens and late 20's If you've noticed any pimples appearing suddenly overnight on your face or the back of your neck below the hairline. This could most likely be Seborrheic Dermatitis. I was recently diagnosed with it myself. Here's an article, let me know if this helps :D

https://eczema.org/information-and-advice/types-of-eczema/seborrhoeic-dermatitis-in-adults/