What Causes Delayed Periods Having Undergone A Lot Of Stress?

hi, i haven't had my period for a few weeks now. Taken multiple pregnancy tests and they all came out negative. I have been under a lot of stress, don't get a lot of sleep during the week and sometimes maintaing a bad diet during the day because of my schedule. I have always been around 98 pounds and have a really fast metabolism as it is so i know i am not underweight. But i know that all these thigns affect a period. I feel like i have been ovulating because i have discharge and i get the occasional cramps. but im still concerned about my health and if theres is anything else i can do