Anxiety about having an STD

I've had an std before and had no idea i had it until my boyfriend showed symptoms. I got treated for it but never came back within the months to make sure it was gone. I recently had sex with 1 girl and she claimed shes a virgin. I didn't suspect anything because she seemed clean and her vagina didn't smell bad (yes I realize that symptoms can be invisible) and that's the only other person i had sex with other than my bf. I got treated for an sti because I had yellow discharge and i was peeing more frequently. A few days the inside of my vagina was itchy but it went away. My vagina lips get itchy easily. I'm very worried i have an STD. I'm making an appointment to get checked but I'm stressing about it being an std. Any advice or answers are appreciated