What Is The Treatment For Bad Odor Vaginal Discharge?

I hooked up with a guy two nights ago. I performed oral sex on him, but we didn't have intercourse. In the morning I performed oral sex again and his penis smelled a little bit. That day I finished my period. Yesterday my underwear didn't have any stains from discharge but smelled a little like the guy's penis had. Today I had one skinny, light brown streak on my underwear and it smells the same, only very, very, very strong. Do I have an STD or other vaginal infection? My underwear seriously smells horrendous.