Vaginal brown discharge, itching, clusters, and period

Hello. i'm a fifteen year old female, and about a week ago, i noticed that my vagina started itching, there were some white clusters, and eventually, there was a brown discharge. a few days later, my period occured, but my period is still very irregular. a few days BEFORE all of this started, my boyfriend and i had sex. he used a condom. right around the time that my period started, we both went to an anonomis health clinic, and they said that i didn't have any STD's. neither does my boyfriend. do you know what's going on?