What Does Brown Vaginal Discharge Indicate?

I got my period early last month (january 16) i usually get it some time in the 20 s ( i sadly do not remember i had it on a calendar and then my mom threw it away). so after having my period i went to the gynecologist for the first time and found out i had a yeast infection, she gave me the medicine and said to come back two weeks later. about two days before i went to the doctors, i had sex with my boyfriend and we used condoms. the day after having sex i noticed the discharge in my underwear was reddish brownish. i went to the appointment the next day and my doctor told me everything was fine with me that the infection went away. and so i told her about the discharge and how i googled it (which i know is the worst thing you could do) because i knew i couldn t be pregnant because i haven t had sex in a month and she told me that there is nothing wrong with me and if it continues to go see her. the next day it went away so everything was fine. So i thought i would get my period on feb. 16 but i haven t gotten it yet and I m freaking out and over thinking and really stressing out. Ive googled so many things on what could be wrong with me.