The key word in the rule is *QUALIFY*.

If your parents *QUALIFY* to claim you as their dependent, then you have no choice but to indicate on your own tax return that "I can be claimed on someone else's return". It doesn't matter if your parents actually claim you or not.

If your parents qualify to claim you, then my bet is they qualify to claim your newborn too (assuming the baby was actually born in 2019 and not 2020).

I am 19 and filing myself this year

How old you are today doesn't matter. Your age on Dec 31 of the tax year is what matters, along with your student status in 2019. (that includes being a high school student)