Hormonal Changes or STI???

I recently stopped taking my birth control (this is the first month I haven’t taken it). A few days ago I noticed I’ve been more dry down there and have been experiencing some irritation and today I noticed some redness. I do not have any abnormal discharge or odor. I had sex unprotected a little over a week ago. I’ve never experienced this before so I did a few searches and got a variety of possible causes. I have a doctor appt in a few days but I’m just trying to prepare myself. Could it be an STD or has anyone experienced this after stopping birth control?