guilt over melatonin

my 3.5 year old was an amazing sleeper until around 18 months old. since then she’s been sleeping at most 6 hours a night on a good night, no nap. her sleep is always broken up; 2-3hours when she first wakes up then 2-3 hours at around 5am. doctor finally gave us melatonin and i picked it up today now i feel horrible giving it to her. i feel like i failed her and almost like im drugging her to get her to sleep (i know that’s 100% not the case but i can’t help it lol) it doesn’t help that her dad is super against it saying she sleeps well bc he’s never the one up with her.

i have an 18 month old as well and her not sleeping is affecting all of us, i don’t know what to do i feel horrible trying it but i’ve been waiting for this and ill feel worse if it doesn’t help