brown discharge and birth control

I've been on birth control forever now. I'm on the patch. There's zero chance that I'm pregnant or have an std because I haven't had sex with anyone in months and I've gotten my period since and I got tested. So I'm having like weird brown discharge. My period didn't due until next Tuesday and I still a have a patch on. It disappeared so a few minutes ago now I did have sex and everything was fine and now I got to the bathroom and look at my underwear and I see this. This was not in here before I had sex. I don't know what's going on. Should I be concerned ! It does not burn or anything down there I have clear discharge and than here and there brown discharge.