late period!!!!!

guys please help me out i’m so scared. so basically me and my boyfriend ALWAYS have unprotected sex. we’ve only used condoms three times and two of the times where in one night. well we hungout the 3rd and didnt think about anything because i was supposed to start saturday. well saturday changed to sunday and then it changed to monday and now im late. i took a test saturday just to make sure and it was negative but i am freaking myself out to the max. it’s also important to note i am malnourished for my age. i have an eating disorder so i struggle to eat as a regular person would. what can i do to get my period to start?? please help

i know this isn’t the best place to go for this but please advice