Need help: STD?

I have been dating my boyfriend for 8 months and have been specially active no problem. recently about a month ago we went on a “break” and haven’t done anything. a few days ago we had sex again for the first time and after work i had this one sore on the upper part of my inner thigh near my genitalia and it started off being itchy and i thought maybe it was razor burn or an ingrown hair and i scratched the head off of the bump and didn’t think anything of it. now today about 2 days later i got out of the shower and it’s looks like it spread everywhere all over my private and lesions are just everywhere and i’m not sure what i should do but i am freaking out. i’m not sure if he slept w someone else and gave me something he’s saying he didn’t but i am really freaking out