Brown discharge after sex

I had sex with my bf last night and when I went to the bathroom there was weird brown discharge. I thought maybe my period just started early because I’m supposed to get it in 3 days or so, but this morning I checked and I’m not bleeding anymore. Should I be worried? I tried talking to my mom about it and she said I’m fine, but idk this hasn’t happened to me before. I’m not sure if I should go to the doctor or not? Help?