Please help.

Two days ago I had sex with my boyfriend, and today I had a large amount of discharge with an odd odor. I've also recently started birth control, and read that it could be the cause of it. There's a bit of an itch, but I just think it's a razor cut from shaving. Should I be concerned about a possible STD, even though he was tested about 6 months ago, and came back clean? Please help!