Something's wrong with my vagina :(

So I had sex about a week ago with no condom, but I have Nexplanon (the implant). Since then, I have been spotting and my vagina itches like crazy. And I literally mean just my vagina. No other part of my genitalia is irritated. I wasn't spotting at all before I had sex, so I don't know if having sex just made me start spotting, or if it's something bad. There's no weird discharge or smell and my guy and I don't have any STDs.